dual temp gauges
My 1983 vintage twin 120 lehman Grand Banks has dual temp gauges for each engine.
For the past few years I have fought a problem with the port temp gauges. Every once in a while the upper and lower helm station gauges jump up and read high. Sometimes by banging on the lower gauge the temps will suddenly jump back to a correct reading.
I have checked and rechecked wiring and it seems solid. I suspect there is something wrong with the lower helm station gauge itself. To prove it is not the sender, wiring and upper gauge can I just disconnect the wires to the lower gauge and use only the upper helm station gauge for a few weeks?
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No I'm sure that would not work. The sending unit is a dual gauge unit that
has to have two gauges in series that have the correct resistance to read
the correct temp.
Actually what you need is a dual sender and matching gauges designed to
work together. You might get lucky and find a replacement gauge that has
the correct resistance. It's best to replace the ending unit and both
gauges by the same manufacturer, all designed to work together.
Guess how I know...
On Saturday, August 26, 2017, Jim Gano via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
My 1983 vintage twin 120 lehman Grand Banks has dual temp gauges for each
engine.
For the past few years I have fought a problem with the port temp gauges.
Every once in a while the upper and lower helm station gauges jump up and
read high. Sometimes by banging on the lower gauge the temps will suddenly
jump back to a correct reading.
I have checked and rechecked wiring and it seems solid. I suspect there
is something wrong with the lower helm station gauge itself. To prove it
is not the sender, wiring and upper gauge can I just disconnect the wires
to the lower gauge and use only the upper helm station gauge for a few
weeks?
Sent from Yahoo Mail on Android
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Unknown
I dont have my schematics in front of me but I thought my gauges were in parallel to the sender.... is that possible?
Sent from Yahoo Mail on Android
On Sat, Aug 26, 2017 at 4:37 PM, Dennis Spainrdennisspain@gmail.com wrote: No I'm sure that would not work. The sending unit is a dual gauge unit that has to have two gauges in series that have the correct resistance to read the correct temp.
Actually what you need is a dual sender and matching gauges designed to work together. You might get lucky and find a replacement gauge that has the correct resistance. It's best to replace the ending unit and both gauges by the same manufacturer, all designed to work together.
Guess how I know...
On Saturday, August 26, 2017, Jim Gano via Trawlers-and-Trawlering trawlers@lists.trawlering.com wrote:
My 1983 vintage twin 120 lehman Grand Banks has dual temp gauges for each engine.
For the past few years I have fought a problem with the port temp gauges. Every once in a while the upper and lower helm station gauges jump up and read high. Sometimes by banging on the lower gauge the temps will suddenly jump back to a correct reading.
I have checked and rechecked wiring and it seems solid. I suspect there is something wrong with the lower helm station gauge itself. To prove it is not the sender, wiring and upper gauge can I just disconnect the wires to the lower gauge and use only the upper helm station gauge for a few weeks?
Sent from Yahoo Mail on Android
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It is the resistance on the signal lead that matters.
This is easy to check. Disconnect the signal lead from suspected gauge and
see what the remaining one reads.
Before that however double check ground to the misbehaving gauge. If giving
it a whack makes it work I'm thinking ground not a failing gauge.
On Aug 26, 2017 4:00 PM, "Jim Gano" jim_gano@yahoo.com wrote:
I dont have my schematics in front of me but I thought my gauges were in
parallel to the sender.... is that possible?
Sent from Yahoo Mail on Android
https://overview.mail.yahoo.com/mobile/?.src=Android
On Sat, Aug 26, 2017 at 4:37 PM, Dennis Spain
rdennisspain@gmail.com wrote:
No I'm sure that would not work. The sending unit is a dual gauge unit
that has to have two gauges in series that have the correct resistance to
read the correct temp.
Actually what you need is a dual sender and matching gauges designed to
work together. You might get lucky and find a replacement gauge that has
the correct resistance. It's best to replace the ending unit and both
gauges by the same manufacturer, all designed to work together.
Guess how I know...
On Saturday, August 26, 2017, Jim Gano via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
My 1983 vintage twin 120 lehman Grand Banks has dual temp gauges for each
engine.
For the past few years I have fought a problem with the port temp gauges.
Every once in a while the upper and lower helm station gauges jump up and
read high. Sometimes by banging on the lower gauge the temps will suddenly
jump back to a correct reading.
I have checked and rechecked wiring and it seems solid. I suspect there
is something wrong with the lower helm station gauge itself. To prove it
is not the sender, wiring and upper gauge can I just disconnect the wires
to the lower gauge and use only the upper helm station gauge for a few
weeks?
Sent from Yahoo Mail on Android
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lists.trawlering.com
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A ship in harbor is safe - but that is not what ships are built for. -
Unknown
I have a related problem. I replaced some non-operational gauges on the
fly bridge with units from a surplus store. Now the pilot house gauges
read double values and the fly bridge reads about 1/2. Can I install
resisters in the circuits to avoid buying new, full price gauges.
John
SeaWing
Kent Island, MD
On Sat, Aug 26, 2017 at 4:03 PM, Jim Gano via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
My 1983 vintage twin 120 lehman Grand Banks has dual temp gauges for each
engine.
For the past few years I have fought a problem with the port temp gauges.
Every once in a while the upper and lower helm station gauges jump up and
read high. Sometimes by banging on the lower gauge the temps will suddenly
jump back to a correct reading.
I have checked and rechecked wiring and it seems solid. I suspect there
is something wrong with the lower helm station gauge itself. To prove it
is not the sender, wiring and upper gauge can I just disconnect the wires
to the lower gauge and use only the upper helm station gauge for a few
weeks?
Sent from Yahoo Mail on Android
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On 08/26/2017 06:56 PM, Jim Gano via Trawlers-and-Trawlering wrote:
I dont have my schematics in front of me but I thought my gauges were in parallel to the sender.... is that possible?
Not only possible, but likely. I've never seen dual gauges in series,
always parallel.
That said, it is correct that both gauges must be present and working
for either gauge to read correctly. The sender and the gauges are a
matched set; dual gauges require a dual-gauge sender.
Check all wiring and grounds, and another diagnostic you can do is to
swap the gauges themselves to see if the symptom changes.
If it turns out to be a bad gauge, you need to replace it with an
identical one -- same manufacturer, model, and part number. Otherwise
your only option is to buy a complete set -- dual-gauge sender and two
matched gauges.
-Sean
m/y Vector
lying Charleston, SC
http://OurOdyssey.BlogSpot.com
On 08/26/2017 10:03 PM, John Walsh via Trawlers-and-Trawlering wrote:
... I replaced some non-operational gauges on the
fly bridge with units from a surplus store. Now the pilot house gauges
read double values and the fly bridge reads about 1/2. Can I install
resisters in the circuits to avoid buying new, full price gauges.
The short answer is "no."
The longer answer is that gauges and senders work in matched sets. The
sender has a resistance that varies with the measured value; the
variation is probably not linear and the resistance for the lower and
upper bounds of the measured parameter are unlikely to be the same
between vendors or sometimes even models within the same vendor. The
chances that any given gauge/sender mismatch is as simple as a
resistance offset are extremely remote. In dual-gauge applications, it's
imperative that the gauge movements be identical.
If you want to use discount gauges, make sure you buy the discount
senders that go with them, and for dual-gauge applications you need to
buy two identical gauges designed for that purpose.
-Sean
m/y Vector
lying Charleston, SC
http://OurOdyssey.BlogSpot.com