Electrical problem!
 

So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time but
now dead, sort of... Bill replaced the switch on one and they both worked
until he left town...After another day of meters and torn up galley seems
he's getting 13 volts through the wires but it won't light the bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Measure the resistance of the bulb alone. Then measure the resistance of the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere. If
the wire resistance is 5 ohms in addition to the bulb resistance, you're
looking at a five volt drop in the wires, which is almost the power of the
bulb.

Report the resistances of the wires back to me and I'll walk you through
this.

Magnum

"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time but
now dead, sort of... Bill replaced the switch on one and they both worked
until he left town...After another day of meters and torn up galley seems
he's getting 13 volts through the wires but it won't light the bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

"Seahag" wrote in message ...

Break out a meter. Sounds like a short. If so re-wire.

Joe



So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time but
now dead, sort of... Bill replaced the switch on one and they both worked
until he left town...After another day of meters and torn up galley seems
he's getting 13 volts through the wires but it won't light the bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Thanks, sounds like you have a clue! We're just having coffee so it will be
awhile before we start tearing out stuff.

Seahag

"Magnum" wrote:
Measure the resistance of the bulb alone. Then measure the resistance of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere. If
the wire resistance is 5 ohms in addition to the bulb resistance, you're
looking at a five volt drop in the wires, which is almost the power of the
bulb.

Report the resistances of the wires back to me and I'll walk you through
this.

Magnum

"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

If you've got 13 volts at the light bulb end of the wires, then the problem
could be:
1. faulty light bulb(s).
2. faulty light socket(s) (perhaps oxide has built up on the bulb, the
socket, or the wire ends, which could be the resistance you mentioned).
3. faulty light switch(es) (pull the bulb out and check voltage at the
socket; make sure the switch is in the ON position).
4. loose wire (make sure all terminals are oxide free and tight. Since you
have more than one light in this circuit, I'm going to assume they daisy
chain (jumper) from one fixture to the next, make sure all wires are secure
on all 4 fixtures.
Scout


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time but
now dead, sort of... Bill replaced the switch on one and they both worked
until he left town...After another day of meters and torn up galley seems
he's getting 13 volts through the wires but it won't light the bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

use your meter, don't tear anything apart unless the meter indicates the
need to tear out!
Scout

"Seahag" wrote in message
...
Thanks, sounds like you have a clue! We're just having coffee so it will
be
awhile before we start tearing out stuff.

Seahag

"Magnum" wrote:
Measure the resistance of the bulb alone. Then measure the resistance of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere.
If
the wire resistance is 5 ohms in addition to the bulb resistance, you're
looking at a five volt drop in the wires, which is almost the power of
the
bulb.

Report the resistances of the wires back to me and I'll walk you through
this.

Magnum

"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit have
been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Clean the bulb base and fixture contact area.
Reinstall bulb with some dielectric grease to
prevent corrosion. The grease won't act as an
insulator. The pressure of the contact will
displace it.

If that does not work try new bulbs.

If not that, I'd check the wires to the fixture.
Chances are good there is corrosion where
the house wiring meets the fixture wiring.



"Seahag" wrote

So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time but
now dead, sort of... Bill replaced the switch on one and they both worked
until he left town...After another day of meters and torn up galley seems
he's getting 13 volts through the wires but it won't light the bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Joe, wouldn't a short drain the battery or blow the fuse?

Magnum


"Joe" wrote in message
om...
"Seahag" wrote in message
...

Break out a meter. Sounds like a short. If so re-wire.

Joe



So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Thanks. Just what I was thinking. The new 20w. halogen bulb alone is 0.9
average. The resistance on the ground side is 1.5 ohms. The ground side got
interesting today, I had the terminal strip unhooked to do these tests when
Haggy went to take a shower and there was no water. Why do they use only
one ground circuit for the whole boat? Well I hooked back up... ah marital
bliss restored!

The positive side gives me 255K ohms! I guess we know where the problem is.
Too bad the wires are forever berried in epoxy. I have the saw out. Stay
tuned.

Mr. H.


"Magnum" wrote:

Measure the resistance of the bulb alone. Then measure the resistance of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere. If
the wire resistance is 5 ohms in addition to the bulb resistance, you're
looking at a five volt drop in the wires, which is almost the power of the
bulb.

Report the resistances of the wires back to me and I'll walk you through
this.

Magnum

"Seahag" wrote:
So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

so it's working now? what was the problem?
Scout

"Seahag" wrote in message
...

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the bulb, the
socket, or the wire ends, which could be the resistance you mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage at the
socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight. Since
you
have more than one light in this circuit, I'm going to assume they daisy
chain (jumper) from one fixture to the next, make sure all wires are
secure
on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about that!

Seahag


Scout


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit have
been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

No, now they're out full time:^)

Seahag

"Scout" wrote:
so it's working now? what was the problem?
Scout

"Seahag" wrote in message
...

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the bulb, the
socket, or the wire ends, which could be the resistance you
mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage at the
socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight. Since
you
have more than one light in this circuit, I'm going to assume they
daisy
chain (jumper) from one fixture to the next, make sure all wires are
secure
on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about that!

Seahag


Scout


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit have
been
giving me the blues for a month or so. Intermittant most of the
time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Well IMHO, that is better than an intermittent problem!
If you've got 13 volts at the bulb and a good 12 volt bulb, what's left?
Scout

"Seahag" wrote in message
...
No, now they're out full time:^)

Seahag

"Scout" wrote:
so it's working now? what was the problem?
Scout

"Seahag" wrote in message
...

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the bulb,
the
socket, or the wire ends, which could be the resistance you
mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage at
the
socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight.
Since
you
have more than one light in this circuit, I'm going to assume they
daisy
chain (jumper) from one fixture to the next, make sure all wires are
secure
on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about that!

Seahag


Scout


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit
have
been
giving me the blues for a month or so. Intermittant most of the
time
but
now dead, sort of... Bill replaced the switch on one and they
both
worked
until he left town...After another day of meters and torn up
galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Not sure yet, did you read Mr.H's post on this thread from last night? He's
preparing to try to check the wires where they cross over the stove area...

Seahag

"Scout" wrote:
Well IMHO, that is better than an intermittent problem!
If you've got 13 volts at the bulb and a good 12 volt bulb, what's left?
Scout

"Seahag" wrote:
No, now they're out full time:^)


"Scout" wrote:
so it's working now? what was the problem?
Scout

"Seahag" wrote:

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then
the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the bulb,
the socket, or the wire ends, which could be the resistance you
mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage at
the socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight.
Since you
have more than one light in this circuit, I'm going to assume they
daisy
chain (jumper) from one fixture to the next, make sure all wires
are
secure on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about that!


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit
have been
giving me the blues for a month or so. Intermittant most of the
time but
now dead, sort of... Bill replaced the switch on one and they
both worked
until he left town...After another day of meters and torn up
galley seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any
ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

"Seahag" wrote
The new 20w. halogen bulb alone is 0.9 average.

..9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160 watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.


The resistance on the ground side is 1.5 ohms.
from where to where? from the grounded terminal strip to the ground side of
the bulb socket? That should be closer to zero, but again, I don't know how
accurate your meter is.

The positive side gives me 255K ohms!
Again, measuring from what point to what point?
One way to double check this before you rip anything apart, is to take a new
piece of clean, adequately sized wire (14-16 gauge), long enough to reach
from the fuse or breaker panel that feeds the lights, and do the following:
1. check the resistance of the new wire (it should be very close to zero
ohms).
2. disconnect the positive wire from the light fixture and twist one end of
the new wire to the now disconnected fixture wire. make sure they are clean
and tight.
3. run the other end of the new wire back to the fuse or breaker panel.
4. disconnect the suspect wire from the fuse/breaker and connect your ohm
meter to these two free ends.
5. if you show high resistance now, break out your saw or find an alternate
route for your new wire.


I hope this helps. If nothing else, it can confirm suspicions before ripping
apart anything. I'm a bit concerned about that meter though.
Scout



Too bad the wires are forever berried in epoxy. I have the saw out. Stay
tuned.

Mr. H.


"Magnum" wrote:

Measure the resistance of the bulb alone. Then measure the resistance of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere.
If
the wire resistance is 5 ohms in addition to the bulb resistance, you're
looking at a five volt drop in the wires, which is almost the power of
the
bulb.

Report the resistances of the wires back to me and I'll walk you through
this.

Magnum

"Seahag" wrote:
So the aft-most two dome lights (12 volt) on a 4 light circuit have
been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

just saw it now and replied.
Scout

"Seahag" wrote in message
...
Not sure yet, did you read Mr.H's post on this thread from last night?
He's
preparing to try to check the wires where they cross over the stove
area...

Seahag

"Scout" wrote:
Well IMHO, that is better than an intermittent problem!
If you've got 13 volts at the bulb and a good 12 volt bulb, what's left?
Scout

"Seahag" wrote:
No, now they're out full time:^)


"Scout" wrote:
so it's working now? what was the problem?
Scout

"Seahag" wrote:

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then
the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the
bulb,
the socket, or the wire ends, which could be the resistance you
mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage
at
the socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight.
Since you
have more than one light in this circuit, I'm going to assume
they
daisy
chain (jumper) from one fixture to the next, make sure all wires
are
secure on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about
that!


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit

have been
giving me the blues for a month or so. Intermittant most of
the
time but
now dead, sort of... Bill replaced the switch on one and they
both worked
until he left town...After another day of meters and torn up
galley seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any
ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Perhaps resistance increases with temperature as it does with almost all
metals.?

Unless the bulb element is made with germanium.

Good going Mr. Hag! Watch out for ground resistance. Daisy chaining ground
wires can give you high ground resistance, or large voltage drops especially
when other circuits draw a big current. If you use multiple devices on the
same ground wire make sure the ground wire is rated for the sum of all the
currents from each device.




"Scout" wrote in message
...
"Seahag" wrote
The new 20w. halogen bulb alone is 0.9 average.

.9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160
watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.


The resistance on the ground side is 1.5 ohms.
from where to where? from the grounded terminal strip to the ground side
of
the bulb socket? That should be closer to zero, but again, I don't know
how
accurate your meter is.

The positive side gives me 255K ohms!
Again, measuring from what point to what point?
One way to double check this before you rip anything apart, is to take a
new
piece of clean, adequately sized wire (14-16 gauge), long enough to reach
from the fuse or breaker panel that feeds the lights, and do the
following:
1. check the resistance of the new wire (it should be very close to zero
ohms).
2. disconnect the positive wire from the light fixture and twist one end
of
the new wire to the now disconnected fixture wire. make sure they are
clean
and tight.
3. run the other end of the new wire back to the fuse or breaker panel.
4. disconnect the suspect wire from the fuse/breaker and connect your ohm
meter to these two free ends.
5. if you show high resistance now, break out your saw or find an
alternate
route for your new wire.


I hope this helps. If nothing else, it can confirm suspicions before
ripping
apart anything. I'm a bit concerned about that meter though.
Scout



Too bad the wires are forever berried in epoxy. I have the saw out.
Stay
tuned.

Mr. H.


"Magnum" wrote:

Measure the resistance of the bulb alone. Then measure the resistance
of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere.
If
the wire resistance is 5 ohms in addition to the bulb resistance,
you're
looking at a five volt drop in the wires, which is almost the power of
the
bulb.

Report the resistances of the wires back to me and I'll walk you
through
this.

Magnum

"Seahag" wrote:
So the aft-most two dome lights (12 volt) on a 4 light circuit have
been
giving me the blues for a month or so. Intermittant most of the
time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

And you teach electricity?

Magnum, man of lightning!

"Scout" wrote in message
...
Well IMHO, that is better than an intermittent problem!
If you've got 13 volts at the bulb and a good 12 volt bulb, what's left?
Scout

"Seahag" wrote in message
...
No, now they're out full time:^)

Seahag

"Scout" wrote:
so it's working now? what was the problem?
Scout

"Seahag" wrote in message
...

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then
the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the bulb,
the
socket, or the wire ends, which could be the resistance you
mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage at
the
socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight.
Since
you
have more than one light in this circuit, I'm going to assume they
daisy
chain (jumper) from one fixture to the next, make sure all wires
are
secure
on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about that!

Seahag


Scout


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit
have
been
giving me the blues for a month or so. Intermittant most of the
time
but
now dead, sort of... Bill replaced the switch on one and they
both
worked
until he left town...After another day of meters and torn up
galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any
ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Checking voltages is almost useless because the voltmeter is usually 10 Mega
ohms input impedance or more. It draws no current and will always measure
the open circuit voltage. Resistance is a better measurement or voltage
measured under loaded conditions.
A good battery and a weak battery will give the same voltage reading. They
can't supply the same load current because the weak battery has a higher
internal impedance. Just go and review your Thevinin equivalent circuits.

Magnum

"Scout" wrote in message
...
"Seahag" wrote
The new 20w. halogen bulb alone is 0.9 average.

.9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160
watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.


The resistance on the ground side is 1.5 ohms.
from where to where? from the grounded terminal strip to the ground side
of
the bulb socket? That should be closer to zero, but again, I don't know
how
accurate your meter is.

The positive side gives me 255K ohms!
Again, measuring from what point to what point?
One way to double check this before you rip anything apart, is to take a
new
piece of clean, adequately sized wire (14-16 gauge), long enough to reach
from the fuse or breaker panel that feeds the lights, and do the
following:
1. check the resistance of the new wire (it should be very close to zero
ohms).
2. disconnect the positive wire from the light fixture and twist one end
of
the new wire to the now disconnected fixture wire. make sure they are
clean
and tight.
3. run the other end of the new wire back to the fuse or breaker panel.
4. disconnect the suspect wire from the fuse/breaker and connect your ohm
meter to these two free ends.
5. if you show high resistance now, break out your saw or find an
alternate
route for your new wire.


I hope this helps. If nothing else, it can confirm suspicions before
ripping
apart anything. I'm a bit concerned about that meter though.
Scout



Too bad the wires are forever berried in epoxy. I have the saw out.
Stay
tuned.

Mr. H.


"Magnum" wrote:

Measure the resistance of the bulb alone. Then measure the resistance
of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1 ampere.
If
the wire resistance is 5 ohms in addition to the bulb resistance,
you're
looking at a five volt drop in the wires, which is almost the power of
the
bulb.

Report the resistances of the wires back to me and I'll walk you
through
this.

Magnum

"Seahag" wrote:
So the aft-most two dome lights (12 volt) on a 4 light circuit have
been
giving me the blues for a month or so. Intermittant most of the
time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

"Magnum" wrote in message link.net...
Joe, wouldn't a short drain the battery or blow the fuse?

Magnum

Yeah if she has breakers or fuses. And I think haggy lives aboard so
most likely she uses a contavolt to keep the batteries charged and
carry the house load.




"Joe" wrote in message
om...
"Seahag" wrote in message
...

Break out a meter. Sounds like a short. If so re-wire.

Joe



So the aft-most two dome lights (12 volt) on a 4 light circuit have been
giving me the blues for a month or so. Intermittant most of the time
but
now dead, sort of... Bill replaced the switch on one and they both
worked
until he left town...After another day of meters and torn up galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

"Magnum" wrote
Perhaps resistance increases with temperature as it does with almost all
metals.?


Yes, but they most likely have tungsten elements, and will not see such a
*dramatic* increase in resistance (i.e., .9 to 7+ ohms). That drastic
behavior in an incandescent bulb would be very unusual; methinks the .9 ohm
reading is an error.
Scout

you see an error in that statement?
Scout

"Magnum" wrote
And you teach electricity?

"Scout" wrote in message
Well IMHO, that is better than an intermittent problem!
If you've got 13 volts at the bulb and a good 12 volt bulb, what's left?
Scout

Clearly he does not meet the criteria I've stated, hence he has no light,
which was my point.
Shall I spell it out for you?
Ok, I will: he is missing some aspect in his diagnosis when he states he has
13 volts to a good bulb and it doesn't work. Get it?
Scout

"Magnum" wrote in message
ink.net...
And you teach electricity?

Magnum, man of lightning!

"Scout" wrote in message
...
Well IMHO, that is better than an intermittent problem!
If you've got 13 volts at the bulb and a good 12 volt bulb, what's left?
Scout

"Seahag" wrote in message
...
No, now they're out full time:^)

Seahag

"Scout" wrote:
so it's working now? what was the problem?
Scout

"Seahag" wrote in message
...

"Scout" wrote:
If you've got 13 volts at the light bulb end of the wires, then
the
problem
could be:
1. faulty light bulb(s).

Did that.

2. faulty light socket(s) (perhaps oxide has built up on the
bulb,
the
socket, or the wire ends, which could be the resistance you
mentioned).

Did that.

3. faulty light switch(es) (pull the bulb out and check voltage
at
the
socket; make sure the switch is in the ON position).

Did that.

4. loose wire (make sure all terminals are oxide free and tight.
Since
you
have more than one light in this circuit, I'm going to assume
they
daisy
chain (jumper) from one fixture to the next, make sure all wires
are
secure
on all 4 fixtures.

Did that. No longer intermittant. Bill's really happy about
that!

Seahag


Scout


"Seahag" wrote in message
...
So the aft-most two dome lights (12 volt) on a 4 light circuit
have
been
giving me the blues for a month or so. Intermittant most of
the
time
but
now dead, sort of... Bill replaced the switch on one and they
both
worked
until he left town...After another day of meters and torn up
galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any
ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

Have you read his post carefully? He has stated the high resistance in the
other line, not the ground leg.
Scout

"Magnum" wrote
Good going Mr. Hag! Watch out for ground resistance.

I'm not sure to whom you are replying but I'll toss in another 2 cents. If
the bulb is good, as he has stated, and the rest of the circuit is intact,
then a voltmeter is appropriate. True, a voltage reading without a load can
be misleading, but it also a piece in the diagnostic puzzle. Had he the 13
volts present without the bulb (i.e., measured at the fixture's terminals)
and lost the voltage when the bulb was subsequently plugged in, then I would
say he has a complete circuit (proven by the first reading) which is unable
to sustain the current, and therefore the potential, possibly do to a high
resistance in the circuit or a faulty power supply (I think we are all
assuming the power supply is not the problem, however).
Scout

"Magnum" wrote in message
ink.net...
Checking voltages is almost useless because the voltmeter is usually 10
Mega
ohms input impedance or more. It draws no current and will always measure
the open circuit voltage. Resistance is a better measurement or voltage
measured under loaded conditions.
A good battery and a weak battery will give the same voltage reading. They
can't supply the same load current because the weak battery has a higher
internal impedance. Just go and review your Thevinin equivalent circuits.

Magnum

"Scout" wrote in message
...
"Seahag" wrote
The new 20w. halogen bulb alone is 0.9 average.

.9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160
watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.


The resistance on the ground side is 1.5 ohms.
from where to where? from the grounded terminal strip to the ground side
of
the bulb socket? That should be closer to zero, but again, I don't know
how
accurate your meter is.

The positive side gives me 255K ohms!
Again, measuring from what point to what point?
One way to double check this before you rip anything apart, is to take a
new
piece of clean, adequately sized wire (14-16 gauge), long enough to
reach
from the fuse or breaker panel that feeds the lights, and do the
following:
1. check the resistance of the new wire (it should be very close to zero
ohms).
2. disconnect the positive wire from the light fixture and twist one end
of
the new wire to the now disconnected fixture wire. make sure they are
clean
and tight.
3. run the other end of the new wire back to the fuse or breaker panel.
4. disconnect the suspect wire from the fuse/breaker and connect your
ohm
meter to these two free ends.
5. if you show high resistance now, break out your saw or find an
alternate
route for your new wire.


I hope this helps. If nothing else, it can confirm suspicions before
ripping
apart anything. I'm a bit concerned about that meter though.
Scout



Too bad the wires are forever berried in epoxy. I have the saw out.
Stay
tuned.

Mr. H.


"Magnum" wrote:

Measure the resistance of the bulb alone. Then measure the
resistance
of
the
wires with the bulb in the socket from the circuit breaker or power
connection. If the bulb is, for instance, 12 watts, it draws 1
ampere.
If
the wire resistance is 5 ohms in addition to the bulb resistance,
you're
looking at a five volt drop in the wires, which is almost the power
of
the
bulb.

Report the resistances of the wires back to me and I'll walk you
through
this.

Magnum

"Seahag" wrote:
So the aft-most two dome lights (12 volt) on a 4 light circuit
have
been
giving me the blues for a month or so. Intermittant most of the
time
but
now dead, sort of... Bill replaced the switch on one and they
both
worked
until he left town...After another day of meters and torn up
galley
seems
he's getting 13 volts through the wires but it won't light the
bulb...He's
thinking there is some sort of resistance somewhere. Any ideas?
Experience? Jokes?? The Taiwanese in their infinite wisdumb
epoxied
the
wires into the deck beams and cabin sides!!!

Seahag
(Dinner's on before dark!)

no offense Magnum,
but it seems you could use a brush up in your electrical skills.
Scout

"Magnum" wrote
And you teach electricity?

Magnum, man of lightning!

ahh, yes. I stand corrected on that point. Thank you.
Scout

"Magnum" wrote in message
Perhaps resistance increases with temperature as it does with almost all
metals.?

Unless the bulb element is made with germanium.

On Mon, 06 Sep 2004 16:58:56 GMT, "Scout"
wrote this crap:

"Seahag" wrote
The new 20w. halogen bulb alone is 0.9 average.

.9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160 watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.


Anything under 40 ohms is considered a dead short.





Pathetic Earthlings! No one can save you now!

thanks for clearing that up.
Scout

"Horvath" wrote in message
...
On Mon, 06 Sep 2004 16:58:56 GMT, "Scout"
wrote this crap:

"Seahag" wrote
The new 20w. halogen bulb alone is 0.9 average.

.9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160
watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.


Anything under 40 ohms is considered a dead short.





Pathetic Earthlings! No one can save you now!

"Joe" wrote:
"Magnum" wrote:
Joe, wouldn't a short drain the battery or blow the fuse?

Magnum

Yeah if she has breakers or fuses. And I think haggy lives aboard so
most likely she uses a contavolt to keep the batteries charged and
carry the house load.

We have breakers, fuses, and a C-Charger 5000 series charger as well as a
galvanic isolater (something like that anyway).

Seahag

"Seahag" wrote in message ...
"Joe" wrote:
"Magnum" wrote:
Joe, wouldn't a short drain the battery or blow the fuse?

Magnum

Yeah if she has breakers or fuses. And I think haggy lives aboard so
most likely she uses a contavolt to keep the batteries charged and
carry the house load.

We have breakers, fuses, and a C-Charger 5000 series charger as well as a
galvanic isolater (something like that anyway).

Seahag


So....Did ya find the problem?

Joe

if that doesn't warrant a whoop, then I ask you: what does?
Scout

"Seahag" wrote
[snip] With a whoop of delight he put on a new butt connecter

You eally want to announce that he was involved with a butt connection?
"Scout" wrote in message
...
if that doesn't warrant a whoop, then I ask you: what does?
Scout

"Seahag" wrote
[snip] With a whoop of delight he put on a new butt connecter

have 2 answers lined up . . . better judgment kicking in . . .
er...ah...signing off.
Scout

"katysails" wrote in message
...
You eally want to announce that he was involved with a butt connection?
"Scout" wrote in message
...
if that doesn't warrant a whoop, then I ask you: what does?
Scout

"Seahag" wrote
[snip] With a whoop of delight he put on a new butt connecter

Humph, I'll give you two butt connecters!

Seahag

"Scout" wrote:
have 2 answers lined up . . . better judgment kicking in . . .
er...ah...signing off.
Scout

"katysails" wrote:
You eally want to announce that he was involved with a butt connection?
"Scout" wrote:
if that doesn't warrant a whoop, then I ask you: what does?
Scout

"Seahag" wrote
[snip] With a whoop of delight he put on a new butt connecter

WHOOP! ; o)
Scout

"Seahag" wrote in message
...
Humph, I'll give you two butt connecters!

Seahag

"Scout" wrote:
have 2 answers lined up . . . better judgment kicking in . . .
er...ah...signing off.
Scout

"katysails" wrote:
You eally want to announce that he was involved with a butt connection?
"Scout" wrote:
if that doesn't warrant a whoop, then I ask you: what does?
Scout

"Seahag" wrote
[snip] With a whoop of delight he put on a new butt connecter

On Sun, 12 Sep 2004 11:46:30 -0400, "Seahag"
wrote this crap:

Humph, I'll give you two butt connecters!


That's something I would expect Jon-boy to say.





Pathetic Earthlings! No one can save you now!

"Horvath" wrote in message
...
On Sun, 12 Sep 2004 11:46:30 -0400, "Seahag"
wrote this crap:

Humph, I'll give you two butt connecters!


That's something I would say.





Pathetic Earthlings! No one can save you now!

"Horvath" wrote this crap:

Humph, I'll give you two butt connecters!


That's something I would love Jon-boy to say to me.



athetic !

WHOOPEEEEE!!!!!!!
Scout

"Seahag" wrote in message
...
Humph, I'll give you two butt connecters!

Seahag

"Scout" wrote:
have 2 answers lined up . . . better judgment kicking in . . .
er...ah...signing off.
Scout

"katysails" wrote:
You eally want to announce that he was involved with a butt
connection?
"Scout" wrote:
if that doesn't warrant a whoop, then I ask you: what does?
Scout

"Seahag" wrote
[snip] With a whoop of delight he put on a new butt connecter

Horvath wrote:

On Mon, 06 Sep 2004 16:58:56 GMT, "Scout"
wrote this crap:


"Seahag" wrote

The new 20w. halogen bulb alone is 0.9 average.

.9 Ohms? If so, something is wrong here, perhaps with your meter. At .9
ohms, given a 12 volt supply, that bulb would draw 13.3 amps (or 160 watts).
A 20w bulb should have an ohm reading of about 7.2 ohms.



Anything under 40 homos is considered a dead short.





Pathetic Earthlings! No one can save you now!