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Author Topic: Engine water temp gauge comparison - Suggestions?  (Read 587 times)
Gordie Allen
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« on: March 08, 2013, 05:36:02 PM »

I'm wiring my dash from Custom Instrument Panels.  I used the sending units they provided, but I suspected the H2O temp gauge was reading low, so I added a manual gauge in the engine compartment.  When the manual gauge reads 150, the electric only reads 130.  I haven't run it long enough to get it up to 180.  It's winter in Michigan, and I'm about a week away from actually getting it on the road.  Should I replace the 14 AWG with 10, or try a different sending unit?  OR are there other options?
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Augusta, MI
1956 4104
DD 671
lostagain
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« Reply #1 on: March 08, 2013, 05:42:37 PM »

I would shoot the thermostat housings with an IR gun. Maybe your dash electric gauge is alright, and your mechanical one is wrong? And don't sweat it too much until you reach 180F.

JC
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JC
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Len Silva
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« Reply #2 on: March 09, 2013, 06:59:20 AM »

Temperature gauges will typically read high, not low, if there is an electrical problem.  There should be no reason to run larger than 16 ga to the sender.

Check the gauge manufacturers resistance chart.  It will tell you the expected resistance at the sender for various temperatures.  You can then substitute an ohmmeter for the gauge and compare it to the mechanical/infrared temps.

I would not spend time or money changing parts at random, this is a pretty simple problem to fix right.
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« Reply #3 on: March 09, 2013, 07:21:57 AM »

The older buses have resistance loops in the system find it and play around with the loops electric gauges can be made to read accurate with out a lot of time and trouble

good luck
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Gordie Allen
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« Reply #4 on: March 09, 2013, 01:16:40 PM »

Thanks guys.  I checked the manual gauge with boiling water.  It reads right on the money, so I've got an accurate reference for the electric gauge.  Glad to know ahead of time that bigger wire won't help.
Gordie
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Augusta, MI
1956 4104
DD 671
gus
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« Reply #5 on: March 09, 2013, 02:39:05 PM »

Loosen the sender on the engine just a bit and re-tighten it to clean the threads.

Also loosen and re-tighten the wire to the sender, these things corrode. Also make sure the wire isn't frayed with broken strands going into the connector.

I replaced mine with a digital gage and new sender, it is right on the money now so my old sender was either bad or not making good contact. Used the same old wires.
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Gordie Allen
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« Reply #6 on: March 09, 2013, 02:53:29 PM »

ALL the wiring is new as is the sending unit.  I'll loosen and tighten it and check the other connections.
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Augusta, MI
1956 4104
DD 671
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