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Default Volvo Penta 2002B 18 HP Deluxe Panel Temp Gauge

On Thu, 8 Apr 2010 06:46:02 -0400, "Armond Perretta"
wrote:

Bruce wrote:

As far as the instrument problem is concerned the logical plan would
be to undo the last thing done, i.e., disconnect the Tach and see what
happens?

Hardly rocket science but if only one thing changes - the bloke
connects a different tachometer - and all the instruments fail then


Which I will of course try today. Yesterday I tried switching the old tach
wires (see original post). That was a "no go" because the connectors allow
only one proper connection on the new instrument. Note that only the temp
gauge is acting up. All other gauges (oil, voltage, tach, alarms, lights,
etc.) perform properly.


Still, I'd reverse my "repair" and see what happens. A heat gage going
full scale indicates that somewhere between the instrument the temp.
sender you have a short to ground and/or the sender in shorted to
ground.

You can isolate things a bit more by disconnecting the existing
connections to the Temp. Gage and connecting a jumper from some known
source of power to the proper terminal on the gage, then temporarily
connect the wire from the temp sender, to the gage and see how it
works.Try using a jumper of some sort, make a whole new connection
from the gage to the sender and see what happens. This should give you
a pretty good indication of what is working and what is not. If you
find that isolated from everything else on the panel the Temp Gage
works then you can investigate the "everything else".

And yes, this is exactly, leaving out experience, how a professional
instrumentation guy will do it - isolate the instrument and it's
sender from everything else to determine whether it is the instruments
themselves or "everything else", fix either the instrument or
"everything else".


Cheers,

Bruce
(bruceinbangkokatgmaildotcom)
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Default Volvo Penta 2002B 18 HP Deluxe Panel Temp Gauge

On Thu, 08 Apr 2010 22:34:24 +0100, goofball_star_dot_etal
wrote:

On 08/04/2010 08:39, Bruce wrote:
On Wed, 07 Apr 2010 14:59:02 +0100, goofball_star_dot_etal
wrote:

On 07/04/2010 14:14, Bruce wrote:
On Tue, 06 Apr 2010 23:49:41 +0100, goofball_star_dot_etal
wrote:

On 06/04/2010 21:33, goofball_star_dot_etal wrote:
On 06/04/2010 21:04, Armond Perretta wrote:
My 2002 (1993) has 3700 hours and runs well. The deluxe panel also was
fine
with all gauges except the tach performing properly. I have replaced the
original tach with the latest (both wires removed from the old sender and
one of these to "w" on the alternator, the hour meter wire removed and
set
aside, etc.). I just started up the engine for the upcoming season and
the
new tach is fine. However now I have a new issue with the temp gauge.
Here
are the symptoms.

Prior to starting, when I turn the key one click, all gauges including
the
temp move a bit, indicating that the wiring is fine to all instruments.
Nothing happens with the tach of course. When I then start up, all gauges
including the new tach perform as designed, except that the old temp
gauge
(which ran perfectly last year) pegs to the left once the engine starts,
giving what looks like reverse polarity connection symptoms. I did not
change any wiring to this gauge when fitting the new tach.

Next, when I shut down after running the engine under load and letting it
come to temp, all the gauges including the temp show what appear to be
correct readings, but only when the engine is NOT actually running.
That is,
it seems the temp sender is OK and sending correct info, the oil sender
same, the voltage meter same, the tack off of course, etc. I think this
means the temp sender is fine, but that running the engine is somehow
sending the incorrect voltage to the meter. Only when I start up and the
engine is actually running (and the tach showing the revs) does the temp
gauge peg to the left. Is it possible I just picked the wrong one of
the 2
old tach wires for the new tach to connect to "w"? No other wiring
changed
from the time the temp gauge was OK. Ideas welcomed.


Check for voltage drops between various earth points when the alternator
is charging.

In particular, check the integrity of the alternator earth path (since
it seems that the error is associated with charging current), the engine
earth path (since, probably, the temperature sensor thermistor uses the
engine as earth), and the instrument earth (since that is where you see
the problem). In an ideal world one would have a single point earth but
this is not always practical.

I'm a bit confused. Assuming a normal inboard engine installation, the
alternator earth is normally either through the case to the engine
block or through a separate earth connection to the same place. The
engine is normally grounded/earthed by a direct connection back to the
negative side of the battery.

It almost has to be connected this way as the starter, which IS
earthed through its case to the engine block will never develop its
normal power without an adequate earth/ground path back to the power
source; the battery.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Fortunately the starter is not running, so does effectively does not
exist during normal operations. I bet some meters kick when the starter
is operated on many boats..
There comes a point when it is quicker to get a meter out and fix the
problem rather than to speculate what should be, or might be. It stinks
of a 'common mode' problem to me, and I would check the earth conections
first. I look forward to hearing the result.


I was commenting on the remark about multiple ground circuits, as
there aren't any. The Temp and pressure senders are grounded through
their case to the engine block. The alternator is grounded through its
case to the engine block.The starter is grounded through its case to
the engine block. If an electrical ignition engine the ignition is
grounded to the engine block. The engine block is grounded through a
big cable to the battery Neg. post. No multiple paths.


Some common paths there, and the possibility of a connection not being
as it should be. If there is a potential difference between the sender
earth (ground) and the instrument earth, it might cause the observed
problem if there are two legs of a bridge circuit which go to different
'earths'. There is no such thing as a single point (earth). Whether an
engine block, terminal block, star washer, or other connection can be
treated as electrically equivalent to one is what matters. It depends on
the circumstances, such as the frequency and the currents involved etc.
Mixing sensitive instruments with high current devices such as starter
motors by sharing a common path (wire) is not a good idea for the poor
instrument, but it well may be ok for two intruments to be connected
through a shared supply wire. For RF interference issues, a low
resistance is no guide to whether a connection is low impedance or can
be regarded as a single point.


As far as the instrument problem is concerned the logical plan would
be to undo the last thing done, i.e., disconnect the Tach and see what
happens?

Can't do any harm.

Hardly rocket science but if only one thing changes - the bloke
connects a different tachometer - and all the instruments fail then
????.


Then there is a fault. We knew that. Tachometers don't wreck temperature
gauges all on their own. He may have inadvertently disturbed something
or connected wires at random but I was trying to suggest something that
he may not already have thought of, rather than the most likely cause
(finger trouble..)



Of course is one or more "sending units" are not properly grounded
then that instrument will not read correctly but that is not a
multiple ground path, which I was replying to. It is a poor or
nonexistent connection to the common ground.

with most 3rd party tachometers it is very possible to connect them
improperly as many times the marking is ambiguous (unless one actually
reads the instructions :-) I once came across a temp gage set with the
gage marked "+", "I" and one extra pigtail with no marking. The sender
had two terminals, one marked "W" and the other unmarked. It turned
out that the gage body was grounded through its mount and the pigtail
was the light "I" was connected to the unmarked terminal on the sender
and "W" was a warning circuit.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)
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Default Volvo Penta 2002B 18 HP Deluxe Panel Temp Gauge

Bruce wrote:

... I'd reverse my "repair" and see what happens. A heat gage going
full scale indicates that somewhere between the instrument the temp.
sender you have a short to ground and/or the sender in shorted to
ground.
...
... this is exactly, leaving out experience, how a professional
instrumentation guy will do it - isolate the instrument and it's
sender from everything else to determine whether it is the instruments
themselves or "everything else", fix either the instrument or
"everything else".


Thanks, Bruce. I think I am getting close to a solution for this issues
thanks to many comments here, on the Volvo forums, and elsewhere. I am
betting that I simply removed the wires from the temp sender when trying to
remove the wires from the tach sender. My manuals and Volvo downloads give
essentially no exact guidance, pictures, or diagrams on which sensor is
which, and on top of that there is really no room in the engine compartment
to look around and see the entire layout. This of course has been a problem
from day one with small sailing boats.

I just sent the following to the Volvo forum. Additional comments are of
course welcome. BTW thanks to you all who are providing serious and
detailed suggestions. I readily admit I am an amateur when it comes to
marine diesels, despite having messed with them 30 or so years. Apparently
some few readers believe it's necessary to remind me of my ignorance in
these matters. Rest assured, friends and others, I am well aware of my
limitations and have been humbled by the sea many times.

Set to Volvo forums:

"I think we're getting warm. Yesterday I tried various combinations,
including just disconnecting the wire to the "w" lug. I had assumed that
this wire, one of 2, belonged to the old tach. When I then tried the engine
with this wire disconnected the tach still worked but the temp gauge was
"dead."

"In other words I suspect that my problem is that instead of disconnecting
the wires I may have mistakenly assumed belonged to the old tach, I actually
disconnected the wires from the temp sender, and then connected one of these
to "w" on the alternator. This fits all the symptoms so far, and could
easily have happened since I am not really sure which sender is temp and
which is revs. My manual does not show the locations clearly. Another clue
is that the pair I disconnected has 2 different sized lugs, fitting the
description of the temp sender wires given to me by Richard Vosbury of
Annapolis. I suspect the larger lug is the actual temp resistor and the
smaller lug is the temp alarm.

Today I will run down to the boatyard and try again, this time using the
correct pair of wires (assuming I can locate them somewhere in the vicinity
of the alternator on the starboard side of the engine). In he meantime, any
more comments on these suppositions? Putting all the comments together so
far is at least giving this confused amateur some ideas on how to proceed.
Thanks, gentlemen."

--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://home.comcast.net/~kerrydeare






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Default Volvo Penta 2002B 18 HP Deluxe Panel Temp Gauge

On Fri, 9 Apr 2010 04:14:55 -0400, "Armond Perretta"
wrote:

Bruce wrote:

... I'd reverse my "repair" and see what happens. A heat gage going
full scale indicates that somewhere between the instrument the temp.
sender you have a short to ground and/or the sender in shorted to
ground.
...
... this is exactly, leaving out experience, how a professional
instrumentation guy will do it - isolate the instrument and it's
sender from everything else to determine whether it is the instruments
themselves or "everything else", fix either the instrument or
"everything else".


Thanks, Bruce. I think I am getting close to a solution for this issues
thanks to many comments here, on the Volvo forums, and elsewhere. I am
betting that I simply removed the wires from the temp sender when trying to
remove the wires from the tach sender. My manuals and Volvo downloads give
essentially no exact guidance, pictures, or diagrams on which sensor is
which, and on top of that there is really no room in the engine compartment
to look around and see the entire layout. This of course has been a problem
from day one with small sailing boats.

I just sent the following to the Volvo forum. Additional comments are of
course welcome. BTW thanks to you all who are providing serious and
detailed suggestions. I readily admit I am an amateur when it comes to
marine diesels, despite having messed with them 30 or so years. Apparently
some few readers believe it's necessary to remind me of my ignorance in
these matters. Rest assured, friends and others, I am well aware of my
limitations and have been humbled by the sea many times.

Set to Volvo forums:

"I think we're getting warm. Yesterday I tried various combinations,
including just disconnecting the wire to the "w" lug. I had assumed that
this wire, one of 2, belonged to the old tach. When I then tried the engine
with this wire disconnected the tach still worked but the temp gauge was
"dead."

"In other words I suspect that my problem is that instead of disconnecting
the wires I may have mistakenly assumed belonged to the old tach, I actually
disconnected the wires from the temp sender, and then connected one of these
to "w" on the alternator. This fits all the symptoms so far, and could
easily have happened since I am not really sure which sender is temp and
which is revs. My manual does not show the locations clearly. Another clue
is that the pair I disconnected has 2 different sized lugs, fitting the
description of the temp sender wires given to me by Richard Vosbury of
Annapolis. I suspect the larger lug is the actual temp resistor and the
smaller lug is the temp alarm.

Today I will run down to the boatyard and try again, this time using the
correct pair of wires (assuming I can locate them somewhere in the vicinity
of the alternator on the starboard side of the engine). In he meantime, any
more comments on these suppositions? Putting all the comments together so
far is at least giving this confused amateur some ideas on how to proceed.
Thanks, gentlemen."



Just out of curiosity what are the connections to your tach marked?
You mention "W", but the others?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)
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Default DN RTFM Department

Armond Perretta wrote:
... I think I am getting close to a solution for this issues thanks to
many comments here ... I am betting that I simply removed the wires from
the temp sender when trying to remove the wires from the tach sender ...


The subject line says it all. DO NOT RTFM! Had I ignored the instructions
packaged with the new tach and just switched it out, everything would have
been OK from the beginning. The instructions evidently do not take into
account that during the manufacturing run of this model quite a few changes
were incorporated, including the latest wiring for the tach. Unfortunately
no one in the marketing department was notified that changes in the
brochures were in order. Today I just undid all the changes made according
to the installation literature, essentially just dropped in the replacement
tach, and all works per design.

--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://home.comcast.net/~kerrydeare





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On Fri, 9 Apr 2010 14:02:18 -0400, "Armond Perretta"
wrote:

Armond Perretta wrote:
... I think I am getting close to a solution for this issues thanks to
many comments here ... I am betting that I simply removed the wires from
the temp sender when trying to remove the wires from the tach sender ...


The subject line says it all. DO NOT RTFM! Had I ignored the instructions
packaged with the new tach and just switched it out, everything would have
been OK from the beginning. The instructions evidently do not take into
account that during the manufacturing run of this model quite a few changes
were incorporated, including the latest wiring for the tach. Unfortunately
no one in the marketing department was notified that changes in the
brochures were in order. Today I just undid all the changes made according
to the installation literature, essentially just dropped in the replacement
tach, and all works per design.


Congratulations!
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)
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Default DN RTFM Department

On 09/04/2010 19:02, Armond Perretta wrote:
Armond Perretta wrote:
... I think I am getting close to a solution for this issues thanks to
many comments here ... I am betting that I simply removed the wires from
the temp sender when trying to remove the wires from the tach sender ...


The subject line says it all. DO NOT RTFM! Had I ignored the instructions
packaged with the new tach and just switched it out, everything would have
been OK from the beginning. The instructions evidently do not take into
account that during the manufacturing run of this model quite a few changes
were incorporated, including the latest wiring for the tach. Unfortunately
no one in the marketing department was notified that changes in the
brochures were in order. Today I just undid all the changes made according
to the installation literature, essentially just dropped in the replacement
tach, and all works per design.


Excellent!
I may have underestimated the creativity of your wiring.:-)

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