So I have a problem with my temp gauge - pegs max on start and needle gets hung up on the gauge face bezel.

I pulled the gauge and bench tested it. Using different resistors on the sending unit terminal, I get the correct face reading.

For example, with a 100 ohm resistor and a 12V power supply, I get 220deg F needle position. With a 47 ohm resistor I get 260.

FSM says 55 ohms is 260deg F and 1385 ohms is 100deg F.

On my bench, with the resistor hooked up, if I ground the sender unit lead (like what happens on startup), the needle pegs out and gets stuck on the gauge face bezel.

I tried pushing the needle down or slightly bending the tip. It works a few times then gets stuck again.

When I install the gauge back in the car/cluster, in the run mode, with a cold car (20 deg in NJ this am) it is held at 100 deg on face. When I hit start, it immediately pegs and gets stuck, just like on the bench.

My son has a 1986 IROC and on start, the needle gently sweeps up and down on ignition start. His does not get stuck.

Any ideas what I can do or what my problem is?

 

So I took a grinding wheel and relieved the edge of the gauge so the needle does not hang up when I start the car. I am working on the motor now so did not get it up to temp. It's very cold in NJ. I plan to adjust the TPC and possibly change the IAC so when I get the motor warmed up, I will know if the sending unit is working.

If anyone has experienced the needle hanging up on startup, let me know how/if you addressed it.