Temperature gauge
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
Temperature gauge
I've been struggling with my temperature gauge. 68 L79. My original worked most of last summer than stopped registering. I tested by grounding the sensor wire and the needle moved to the 1 o'clock position. I figured the old gauge was bad. I replaced it with a new gauge with the internal resistor and I have the same result. When the car is upto temperature the gauge reads 100* when i ground the sensor wire it's at the 1 o'clock position. Any thoughts?
Race Director
Joined: Mar 2017
Posts: 11,949
Likes: 4,507
From: Virginia
I've not had to do this, and I have later cars with different gauges, but you may find what you need here:
http://repairs.willcoxcorvette.com/c...re-gauge-info/
Keep scrolling, and you will find info for debugging 68-74 gauges.
http://repairs.willcoxcorvette.com/c...re-gauge-info/
Keep scrolling, and you will find info for debugging 68-74 gauges.
Last edited by Bikespace; Feb 19, 2021 at 04:56 PM.
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
I've not had to do this, and I have later cars with different gauges, but you may find what you need here:
http://repairs.willcoxcorvette.com/c...re-gauge-info/
Keep scrolling, and you will find info for debugging 68-74 gauges.
http://repairs.willcoxcorvette.com/c...re-gauge-info/
Keep scrolling, and you will find info for debugging 68-74 gauges.
Melting Slicks
Joined: Apr 2010
Posts: 2,794
Likes: 1,195
From: Canberra Australia
2025 C3 of the Year Finalist - Modified
I agree the sender is the troublesome part nowadays as many of the reproductions don’t generate the correct ohm load at each temperature.
The way to test the gauge is to give it various ohm loads and see if it deflects properly. Willcox have a great page with all the readings. 1 o’clock on ground does not seem correct mine goes to about 3 o’clock on full grounding of sender.
The old gauge can be tested easy enough, possibly the external resistor has a broken wire, worth a check.
The way to test the gauge is to give it various ohm loads and see if it deflects properly. Willcox have a great page with all the readings. 1 o’clock on ground does not seem correct mine goes to about 3 o’clock on full grounding of sender.
The old gauge can be tested easy enough, possibly the external resistor has a broken wire, worth a check.
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
I agree the sender is the troublesome part nowadays as many of the reproductions don’t generate the correct ohm load at each temperature.
The way to test the gauge is to give it various ohm loads and see if it deflects properly. Willcox have a great page with all the readings. 1 o’clock on ground does not seem correct mine goes to about 3 o’clock on full grounding of sender.
The old gauge can be tested easy enough, possibly the external resistor has a broken wire, worth a check.
The way to test the gauge is to give it various ohm loads and see if it deflects properly. Willcox have a great page with all the readings. 1 o’clock on ground does not seem correct mine goes to about 3 o’clock on full grounding of sender.
The old gauge can be tested easy enough, possibly the external resistor has a broken wire, worth a check.
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
the sending unit is out of the equation. I'm grounding the wire to test the gauge . It's not connected to the sending unit.
Le Mans Master
Joined: Mar 2001
Posts: 6,240
Likes: 1,013
From: Watkinsville, GA and Glen Cove, NY
What happens when you have no sender wire connected? I have a similar problem with my fuel gauge where it seems to be consistently 90 degrees off from where it should be when testing it. That doesn’t apply here, I guess, since you have two gauges doing the same thing. Are you getting full 12 volts at the pink wire, and ground?
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Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
What happens when you have no sender wire connected? I have a similar problem with my fuel gauge where it seems to be consistently 90 degrees off from where it should be when testing it. That doesn’t apply here, I guess, since you have two gauges doing the same thing. Are you getting full 12 volts at the pink wire, and ground?
Thread Starter
Drifting
Joined: Mar 2009
Posts: 1,461
Likes: 361
From: Monson MA
A thought, I did replace the original gauge with a new one that has the internal resistor. I did not install the insulating washer as needed with the original gauge. Could this be my issue?
Le Mans Master
Joined: Mar 2001
Posts: 6,240
Likes: 1,013
From: Watkinsville, GA and Glen Cove, NY
Don’t know as I am not familiar with new gauges, but could be a grounding issue for sure. I would check needle movement with no sender and check pink wire for voltage and check ground
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Your comment that "..it could not be the sending unit, as the gauge does not 'peg out' when grounding the sender wire..." may be incorrect. The assumption you are making is that there is no other form of resistance in the circuit if you ground that wire. But, you only know that the end of that wire is touching chassis ground; you do not know what other 'demons' may be lurking elsewhere in the circuit.
I will state again: If the gauge works at all, it is most likely NOT to be a problem with the gauge. Could it be that the gauge has some kind of mechanical restriction which only allows it to go to the 1 o'clock position? Yes. But that is MOST unlikely (I have never seen such a condition....even when I was working in the metrology laboratories at a major automobile manurfacturer).
I would bet good money that your gremlin lies somewhere in the wiring [or its various connections] of that gauge circuit.
I will state again: If the gauge works at all, it is most likely NOT to be a problem with the gauge. Could it be that the gauge has some kind of mechanical restriction which only allows it to go to the 1 o'clock position? Yes. But that is MOST unlikely (I have never seen such a condition....even when I was working in the metrology laboratories at a major automobile manurfacturer).
I would bet good money that your gremlin lies somewhere in the wiring [or its various connections] of that gauge circuit.