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!)