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Discussion Starter #1
Is there a way to test just my console temperature gauge to see if it's bad?

I have an original gauge that worked years ago before I took the interior out. When everything was put back together, the temperature gauge didn't work ( stayed on C ). It was a little beat up so I figured it had been damaged so I bought a Classic Headquarters replacement gauge from either Rick's or NPD( I don't remember which). This gauge didn't work either ( the needle also never moved from C ).

I have tried three different sending units, all of which are suppose to be for the console gauge. None of them caused the gauge to move when the engine got to 180 degrees. I have checked continuity with the green wire from the sending unit to the gauge and it was fine.

I have been using another temperature gauge outside of the console, but I would really like to use the console gauge.

Any suggestions? I have to think that it's a problem with the gauge itself but it would be nice if there was a test I could do on the gauge to confirm.
 

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You say you checked continuity on the green wire. How did you do that? Did you take a resistance measurement? If so, what was your reading. The reason I ask is that a bad connection will flow current - just not very much current. Bad connections are particulary frustrating because with small loads, they appear just fine, but when the load increases the voltage disappears.

Let's also be sure you have a gauge sender and not a temperature switch used for an idiot light. You should be able to measure the resitance of the sender when cold and see it change considerably as the engine warms up.

Assuming your ohm test of the green wire is good, and that you replaced both the sender and the gauge leaves me to think one of two things is at fault. Either you're not getting power to the gauge or the ground between the gauge, battery, and block is bad.

Use a volt meter to measure from a known good power source to the power terminal on the gauge while the electrical system is powered up. You should see less than a few hundreths of a volt drop in the circuit and also be able to measure full system voltage to ground. Next measure from the block to the gauge ground. Again you should see less than a few hundredths of a volt with the circuit powered up. Keep in mind that the battery (-) pathway to the gauge is important for powering the meter, while the ground path between the block and the gauge is used for the sender return power. It's been reported that too much teflon tape on the sender can insulate it electrically from the block. Measuring the voltage drop between the sender body and the block would reveal the problem - expect less than a few hundreths of a volt drop if all is well there.

One of these tests should point to an open circuit somewhere I suspect.
 

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Discussion Starter #3
I reconnected everything today and confirmed that I had power to the pink wire with the key on. However, when I tested the gauge, the gauge pegged hot.

Here is how I have it wired looking at the back of the gauge:

The bolt at the top ( 12 o'clock ) has nothing connected to it.
The bolt at the bottom ( 6 o'clock) has a ground wire connected to it.

There is a white bar ( resistor?) connecting the bolts at 3 and 9 o'clock.

The bolt on the left ( 9 o'clock) has a connector that is almost horizontal ( pointing toward 3 or 4 o'clock) with the green wire from the sending unit attached.

The bolt on the right ( 3 o'clock) has a connector that is pretty much vertical with the pink wire attached.

Does this sound correct? Any idea what the problem is?
 

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Discussion Starter #4
I think that I am closer.

I have it working where the gauge starts of a little below 'C' and if I connect the green sending unit in the engine compartment to ground, it goes almost all the way to 'H'.

However, when I tested with some hot water and a mechanical gauge, at 190 degrees, it only goes up almost to the 'C'. I was hoping to be at about 1/4 at 190 degrees.

I have three sending units that I have gotten over the years that are all suppose to be correct for the console gauges, however they all give the same result.

Any ideas?
 

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Try connecting the green sending wire to the engine block and see if you get the same full scale reading. If not, you've got a flaky ground between the block and the chassis. Check the ground wire on the right fender if that is the case.
 

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Discussion Starter #6
Thanks I will check the engine block ground, however, I'm not sure that would have impacted my test.

When I tested the gauge in hot water, I had the sending unit out. I connected the sending unit to the negative terminal of the battery with a jumper cable and put the unit in 190 degree water. When I touched the green sending unit wire to the jumper cable, the gauge went almost all the way to 'H' so I think that the ground was OK on my test.

Should the gauge go all the way to 'H' when grounding the green wire? I only got to about 7/8 of the way to 'H'. Maybe there is a problem with my sending unit wire?
 

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Discussion Starter #7
I contacted Rick's tech support and they suggested taking off the needle and putting it back on so that it's on the 'C' when cold ( it was pegged all of the way down when cold).

I did this and when I tested with 190 degree water, the gauge went up to about 1/8th. I guess this is better than nothing but I would like to find a way to get it to go from 'C' up to about 1/4 at 180 - 190 degrees.
 
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