temp gauge problems??

[ptuner11]

60 vette.
Five retail sending units later, I have yet to find one that works correctly. I've sent the gauge and sending unit away to be calibrated....still doesn't work. I replaced the wires and connections...same thing. the needle after a few minutes flips over and pegs hot, but the engine isn't. Besides Delco, I've tried the Wells tu5 , which is touted to be a replacement...no work.
I tried a separate wire from the sending unit to the gauge directly, unhooking the old wire...no change, the needle flips to the hot side. I removed the gauge from the dash and set it up on my bench. I used my battery charger and ran the hot to the gauge. another wire from the other post on the gauge to the top to the sending unit. The negative from the charger to the base of the sending unit. I put the unit in hot water, careful not get the top of it wet. I used an IF heat gun and heated the water(and sending unit) to 180 degrees. I then loosen the small nuts that hold the coils on the gauge in place. I gently moved the coils to all conceivable positions. The needle either stayed on the cold side or abruptly pegged to the hot side, never getting the coils to 'balance' the needle in the middle. i tried all of the new sending units, including the Wells TU5. i just don't get it. i sent this gauge and sending unit to two 'reputable' gauge repair places, one in LA and one back east. they both sent it back saying the gauge is now calibrated, but the gauge still doesn't work.
thanks for any suggestions
ps i'm thinking one of the coils in the gauge is bad. How do I check for a defective coil?

 

[Ken Anderson]

Our company makes the correct sender and it is GM licensed and available from several dealers. Your gauge is mosy likely correct. Ken Anderson

 

[rrhayden]

Ken,

Curious, what company do you work for? I was in the industry for 20 years?

 

[magicv8]

I have a question - are you applying thread sealer or teflon tape to the sender?

If so, remove it.

 

[ptuner11]

dave , thanks for the reply.
there is no pipe dope on the unit.

i have since sent the gauge to :
Corvette Instrument Service
9627 Begonia Street
Palm Beach Gardens, FL 33410
Daytime phone is 561-691-2905

Roger at Corvette instrument service , says that he has the correct sender for the C1. He is calibrating the gauge to the sender. i'm hopeful.

also:
Fred Oliva, Vintage Automotive Research, has been very helpful with some ideas. I'm very thankful for this forum and the helpful people mentioned above. I will keep the thread posted with my results. thanks again.

 

[ptuner11]

i found that inserting a 33 ohm resistor in line on the sending wire was the solution. gauge works great, i tested it with a ir temp gun. As i think back to when this problem started, it was when a mechanic, thinking he was doing a good deed, replaced the last 6 inches of the 'loose' sending unit wire. i'm thinking there might have been a resistor on that piece. i can't think of any other way this problem would have arisen. any way, all's well that ends well. i just wish i didn't buy 6 sending units and send the gauge to 3 different parts of the US to be calibrated.....oh well...........
thanks to Fred Oliva and Strouro... problem solved!!!!!!

 

[Ken Anderson]

The resistor is only a quick fix and only reads ONE correct temp, as the correct sender is calibrated on a curve. When your car actually overheats, you won't know it.

 

[IH2LOSE]

Ken welcome to the forum.

 

[ptuner11]

I have read all the threads about this problem, ie. non linear curve reading of the temp gauge and i was skeptical of this fix. but...
this doesn't seem to be the case here, as i took the time to let the engine over heat...which it does when idleing for a period of time during a 100 plus degree day here, and measure the engine temp with an IF temp gun while reading temp gauge. temp gauge measured adequately thru the over heating stage, ie over 200 degrees. i can't ask for more that that.
As most of the threads on the subject agree, this old style gauge, electromagnetic, is not very accurate. the best that can be hoped for is a somewhat true reading of the higher temps.
I wished I could have fixed this without adding the resistor, but i didn't and i tried it all. this might not be the fix for every one but i feel confident this problem is solved for me.