Mileage

I recently purchased a 1990 coupe 6 spd man. It has a sensor in the head between cylinders 1 and 3. The sensor has a "button" head like a knock sensor. It has a plug on it with the wires snipped off. One red and one black. I can't find any loose wires in the harnesses nearby. Everything seems to work fine, temp gage, fans, ECM etc. The Chevy parts man says the 89's had a "button head" temp sensor in this location. Has someone installed an 89 head on my 90?

ToniH

The driver side alu heads in L98's have the sensor hole in there with or without the fan temp sensor/switch depending on the year. Maybe your head is not original or maybe somebody installed a "low temp switch" to it and later snipped the wires off - who knows? But don't worry, your car should not have one so it doesn't really matter if its there or not.

If you want to search where it might have been connected look at the fan relays in front of the car.

dan0617

I have an '89 and have a temp sensor for the auxiliary fan in that location. It only has one wire, not 2. It is a black wire, on mine. The wire goes to a white plug, that plugs into the sensor. The sensor doesn't have any pigtail or wires or anything on it when it is unplugged.

Mileage

Thanks for the replies. I examined the sensor this morning. It is small in diameter like a temp sensor. As noted everything seems to work fine. When I get a chance I'm going to let it idle without the A/C on to be sure that the fan will come on.

ToniH

This is the aftermarket low temp switch fom MAD:



Look familiar?

Mileage

Yes. Right down to the color of the TWO wires. I will have to research it a bit to see why it may have been installed and the wires snipped flush with the connector