Engine Temp. Gauge Issues

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Brian Bearor

Brian Bearor

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Having an issue with my engine temp gauge. It is slowly showing temp but close to pegging. Temp is no more than 185-195 using a Lazer thermometer.

Replaced the temp sender twice.

Replaced the guage with a new, old stock gauge and same issue.

Cleaned the connections on the plug block as well.

Assuming it is one of the wires.

Before I started changing I thought I would ask the experts if it may be something that isn't obvious before I start down this path.

Thank you for all suggestions.View attachment 1715771273
 
Is the coolant topped up and air burped out? There could be air trapped up near the sender. I believe the gauge would only peg if the lead was grounding out somewhere, but that would be an immediate jump.

*More knowledgeable people may have better answers...
 
Any chance the fuel gauge is also reading a bit high? If so it's likely the regulator called by several names, IVR, instrument limiter, etc. On a non-ralleye dash it plugs into the circuit board. I'd look around and get a modern solid state replacement. Online outfit called RTE is one good one

You can test the gauge system for accuracy by sustituting known resistors for the sender Here is a doctored photo of one type test box, showing the resistors. They are the same for all three gauges (oil if you have one/ ralley)

c-3826-jpg-jpg.jpg


Another way you could go about this is to let the engine warm up to exact middle of scale, then quickly disconnect gauge sender wire and measure sender resistance and see if it is close to what is listed above, 23 ohms for mid scale
 
If you've already replaced the sender twice, be sure you didn't use teflon tape or other sealant on the threads- this can cause intermittent or non-operation. The sending unit MUST be able to ground for the gauge to work. To test, hook an ohmmeter from the body of the sender to a known good ground on the engine block, ohm reading should be at or near 0.
 
And do not overtighten the sender. Use only enough to snug it in and seal it
 
67Dart273 said:
Any chance the fuel gauge is also reading a bit high? If so it's likely the regulator called by several names, IVR, instrument limiter, etc. On a non-ralleye dash it plugs into the circuit board. I'd look around and get a modern solid state replacement. Online outfit called RTE is one good one

You can test the gauge system for accuracy by sustituting known resistors for the sender Here is a doctored photo of one type test box, showing the resistors. They are the same for all three gauges (oil if you have one/ ralley)

View attachment 1715771278

Another way you could go about this is to let the engine warm up to exact middle of scale, then quickly disconnect gauge sender wire and measure sender resistance and see if it is close to what is listed above, 23 ohms for mid scale
Click to expand...
Thanks for the guidance. The fuel gauge is correct. The gauge is pegging it is reading high. Does go up slowly then reads high.
 
theFightingFew said:
Is the coolant topped up and air burped out? There could be air trapped up near the sender. I believe the gauge would only peg if the lead was grounding out somewhere, but that would be an immediate jump.

*More knowledgeable people may have better answers...
Click to expand...

All is good on that end.
 
In that case I don't know. Are the senders you changed the same/ similar manufacture? Maybe they are simply "wrong." Maybe attempt to find another independent sender source

Again, you could check resistance.......When the gauge is heading towards the "overly high" reading, pull the wire off, check sender resistance, and if it indeed is lower than the 10 or so ohms listed for "H" then you know the sender is indeed either sensing a too hot engine or it is erroneously high for the gauge
 
Professor Fate said:
If you've already replaced the sender twice, be sure you didn't use teflon tape or other sealant on the threads- this can cause intermittent or non-operation
Click to expand...
No electrical connection would result in low to no temp. Opposite of the OPs issue.

Assuming your fuel gauge is not doing the same thing then you have some amount of a short in the sender wire.
 
If you remove the sender wire from the sender does the guage read at all?
 
Wild needle swings is a symptom of failing mechanical limiter. I never tried to figure out exactly why this shows more in the temp gauge than in the fuel gauge. Resistance the sender is providing? Length of the circuit? Both? I know current takes the path of least resistance.
In the 73 we had... Gauges worked perfect from cold start. Turn switch off, go in and out of the store, turn switch on again and temp needle would race to high as it could go then slowly fall back to normal reading. No strange behavior in the fuel gauge. Solid state instrument voltage regulator cured it. New mechanical limiter would have cured it. I choose to go solid state.
 
See if the sending wire is shorting somewhere. 0 ohms will peg out the gauge.
 
My temp gauge just started doing the opposite . It will stay on the cold side or not move at all . All wiring was new when car rebuilt , gauges gone thru and solid state limiter .
 
mbaird said:
My temp gauge just started doing the opposite . It will stay on the cold side or not move at all . All wiring was new when car rebuilt , gauges gone thru and solid state limiter .
Click to expand...
With engine at normal operating temp', use ohm meter to check sender resistance signal.
 
mbaird said:
My temp gauge just started doing the opposite . It will stay on the cold side or not move at all . All wiring was new when car rebuilt , gauges gone thru and solid state limiter .
Click to expand...
Could be a stuck open thermostat in your case. New don't matter any more.
 
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