Car overheats because during normal driving the fans do not come on. Temp gauge works fine and shows temperature rising. Turn on A/C, fans engage, temperature goes back to normal.

Replacing ECT sensor, the replacement part (from Advance Auto) has a slightly different size connector. The car'* wiring harness has a single wire to the ECT, and the plug appears to have three terminals.

Decide I may need to wire a new harness if I cannot find correct ECT.

Measure voltage and the wire from harness reads 12 volts. I thought it was supposed to be only 5V.

Does this indicate a problem with the car wiring, or do some ECTs run at 12V?

I am ready to replace the harness connector with a new one that fits available ECT, but need to know if the 12v is a a wiring problem in car (sensor could be good) and will other sensors operate properly at 12V?

Thanks.

Low speed turns on at 212*F, high speed 226*F. Are you sure you are seeing these temps? Temp gauges on these cars are not the most accurate thing on this planet. Best way to test this is to have the car running and disconnect the coolant temp sensor. Low speed fans should automatically turn on regardless of a/c operation or engine temp.

Also, are you sure you have the correct sensor? Can you post pics of the connector on the harness and your new sensor?

Thanks for quick reply.

I returned the sensor and searched locally; no one has the correct part even though their catalogs show they do.

I just placed an order from Rock Auto which had a listing for ACDELCO that appears to have identical connector (blade, pin, single wire). I also ordered a replacement plug.

The plug is currently disconnected while the car waits for the parts. I'll start it up and see if low speed fan is running.

Heres a video I made of the overheating. When I start up the AC, the fans start to spin and the temperature gauge starts to drop. The only problem is the fans aren't activating, afaik. I'm not sure the problem is the sensor because I'm measuring 12v on the pin, where most places say it'* a 5v connection.

This is the part I ordered. Looks the same as one in car.

More Information for ACDELCO 21377

Yeah, like I said, the gauges can be someone misleading. Only way to verify is by using a scantool to see what the PCM is seeing for an actual temperature. Disconnect the temp sensor when the engine is running and see what happens.

On another note, the low coolant light is a sign that your engine is probably drinking coolant. Which is what they are known for. 99% of the time, its the lower intake gaskets.

I ran the car without the temp sensor disconnected. Neither of the fans is running, which suggests another problem. (Both fans run with the AC.)

Because the ECT sensor pin is reading 12V, I think there might be an electrical problem. Why would the low speed fan not come on? It was not up to temp, do I have to drive it some?

Regarding the low coolant light, the coolant in the car is not leaking. Last it was filled was 12 months ago. The dealer wanted to replace the "low coolant sensor" in the radiator, which would have been $450. I told them no way! They claim they couldn't even get the car to overheat like in the video and said both fans were running. It overheats whenever it is driven. Something funny is going on with the dealer.

Above ^ ran the car with the sensor disconnected and the fans did not come on.

This is an OBD 1 car. Does the scan tool hook up to that?

That'* weird. They should come on when that happens. Just to be sure, but you are disconnecting the temp sensor right below the coolant elbow yes?

Umm, no. Its on the top/backside of the block. Let me guess, wrong sensor?

I havent found the schematic for this motor, the closest is the 95 lesabre which has the same motor and shows the sensor on top.

Visual of engine bay didn't show any other sensors with a disconnect of that style.

Are there any online resources for this car? It seems a little bit rare, most of the Regals had the 3.1.