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I've had overheating problems for a while now and I've done almost everything I can think of from changing the water pump, flushing the radiator, changing the thermostat (twice) and changing the cooling temperature sensor (twice). About a month or so ago my mechanic told me he changed some wiring to do with the heat temp sensor, he said it was only sending the fans power on and off. After he did that I changed the cooling temp. sensor again (this being the second time). The first time was a cheaper one and after the fans stopped turning on I bought a more expensive one and put that on after he did the wire work. A week after that the fans stopped turning on again. Even with the fans not running I was okay so long as I was traveling on open highway with higher speeds but last week we went to the drive in and as we were pulling up on the small hill to a straight position from the screen the car started to get hot very fast, mind you we moved the car about three or four times because my b/f can't park a car straight on a hill for w/e reason. When the movies finished and we were leaving to go home the car temp gauge was right at half. I found this very odd to see for a car that had been sitting 2 1/2 + hours but we left and about two miles down the road I had to pull over because the car was getting hot. I could hear a thumping kind of noise from the front bottom of the car. I had to let the car sit for a while and add water to make it home. Ever sense then I can't drive four miles without the car starting to get hot (two lines over half is enough for me to turn the car off considering that is where the last engine temp got before the head gasket blew. I can provide more info about that if needed) whereas before last week I could at least make it around 40 miles before I seen the temp go two lines over half. I have tested the radiator fan by connecting it to the battery and it does turn on but I couldn't get it to run by cross connecting the coolant sensor- to the fan- to the battery but maybe I was doing it wrong since I know little to nothing about vehicles. Is there anything that could be frying the coolant fan sensors I replace? I'm just assuming this one is bad since the fans stopped turning on last week but a week prior when I changed the sensor they were working again albeit short lived. If anyone could tell me how I can fix this problem I would be very grateful!

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contributions: 2002
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Location: Oregon
You have three relays that control the fans. fan control relay 1, mode control relay and fan control relay 2. They work in conjunction with the temp. sensor and the ecm. You need to check to see if the ecm (computer) is sending the signal out to the relays. That is normally done with a scanner hooked up and watching the temp. and fan requests. The scanner could even do a manual test of the relays also. Then you can see if the relays are responding to the ecm commands. I don't know what you mean by "by cross connecting the coolant sensor- to the fan- to the battery" but to make the sensor read full hot you just put a small jumper between the two wires in the connector of the wire harness while it is disconnected from the CTS, (coolant temp. sensor) The fans should turn on in a couple of seconds. You could also turn on the AC and see if the fans come on or not. But there are other things that will affect that too...

Make sure that the cooling system is full of coolant. Water or whatever. If it overheats in just four miles it doesn't sound like the fans are the problem anymore. Check to see how hot your heater gets when the car is hot. If the engine is getting hot but your heater does not seem to be really hot you may have an air pocket and coolant is not circulating. That thumping noise you heard was probably the thermostat slamming closed. You need to check for a damaged head gasket. check for hydrocarbons out of your cooling system. (gas analyzer for measuring emissions)

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