lookingnow

lookingnow not looking anymore! found my vette, a 1996 c4 collector with 6spd,lt4 in great shape (1 loving owner) with ac on stays cool, getting hot in traffic with fans not running. checked how hot idling in garage ac on rad cap off. my temp gauge showed 155f dash ran 185f.i i'm thinking the coolant sensor is off question is witch one controls the fans and where is it?

Kevova

Cooling fans don't until 225 or so. PCM controls fan. Digital temp display on DIC is temp the PCM sees. PCM coolant sensor mounts on water pump.

lookingnow

thanks that is what i was looking for. temp gauge was doing some strange bouncing around going to 285 then dropping to 185, my first thought was sensor engine didn't seem hot . sensor may be a good place to start

MatthewMiller

It sounds like that gauge is intermittently grounding out and pegging itself. I seriously doubt that's an accurate reading of the coolant temp when it bounces around. The stock LT4 calibration on my car had the first fan coming on at 219F in low speeds operation, and the second coming on a 228F. So that's where GM expected the engine to run, normally.

RichS

The sensor on the water pump is for the PCM and LCD readout. This is the temp the fans are controlled by. Both fans will run at low speed then high speed depending temp, or if the a/c is running. The sensor for the analog gauge is on the pass side head between 6 and 8 plugs.