My 85 Z51 4+3 has never displayed a proper temperature in the three years since I bought it. It shows LO all the time, until I shut down the car on a hot day, and when I restart a few minutes later, it shows 160 degrees C, or 320 degrees F. This makes me think instead of a graduated resistance based on temperature, it's simply closing a switch. I can turn on both cooling fans and it goes back to LO in less than a minute. I've used an infrared temperature gun on the engine while running, and pointing it at the thermostat housing shows 185 degrees, and pointing it at the lower rad hose shows 150 degrees.. I believe everything in the cooling system is working properly. I also monitor my oil temperature while this is happening, and it rarely goes above 100 degrees C, or 212 degrees F.

Anyway, I replaced the sensor with a Carquest WTC1049, with no success in getting a realistic temperature display. I then replaced it with a Carquest 85135, with no success. Giving up on Carquest, I put in a NAPA TS6641 sensor, and all it does is show 160 earlier than the Carquest sensors.

Does anyone else have this problem?
Is there a good reliable temperature sensor out there that will deliver an accurate temperature display?

I'm definitely getting tired of hoping I don't have a real problem that I may miss, not having a good display.

 

My 85 is one of the reversed ones. It was easy to check, by grounding the wire on the left head, with ignition on, and hearing the fan start up. So, the right side one for my car is for the gauge. Also, the indication with the last change showed max temperature earlier than the previous ones. It's a little better, but not much.

 

I haven't verified with your method. I've seen the differences between the two brands of senders... The NAPA one is much more sensitive, and displays an overheat condition much more often.
Strange but true...