1988 Chevy Celebrity Cooling fan doesnt come on

grounding the sensor wires are not the thing to do . You may have damaged the computer by doing that. One of them runs the fan and the other the computer except when the a/c is on. First thing is the engine should have been scanned to see if there was a problem. Did you check the correct relay. Also are the sensors getting power? it may not be. Lastly have you jumped the fan to see if they actually work? On the older sensors, they sometimes would leak an dthe corrosion would go up the wire of the sensor giving you the same result. The best bet would be to tes the sensor wire for power and if not probe back until you find it. that may be the problem.

Thanks for the reply hmac300. I didnt know i could damage the computer, i read online that grounding out the two switches will make the fan come on as long as there is no problems with the wiring or relay or fan motor itself. It even said the block switch sould be jumpered out to make the fan run all the time. Im a broke kid, i couldnt afford the $120 they wanted to scan my car. There is 3 large oval relays inside the passenger front fender, i let the engine get up to temp then tried replacing each with the new 1 one at a time, but none of them worked, any tips on finding which is the right one? i cant find my multimeter at the moment, will post results after i do.
how much do sensors cost, would it be worth it to just replace them and cross my fingers that that was the problem?

because you have an OBD1 system on your car, you can scan it yourself. you jump A&B on the aldl which is below the steering column. turn the key on and count the flashes on the service engine light. it will blink 1 time then 2 3 seperat times. that would be a code12. then ifthere are other codes it will blink like 3 then maybe 4 etc. then you come back to the site here under popular site links and look under trouble code definitions. you would look under OBD1 and that will tell you if your sensor is not reading right. Of course if you have disconnected them then you' will have a service engine light on. When you fin dyour multimeter check at the sensor to see ifyou are getting any volts. it should be somewhere around 5 volts. You can go on the site here tosee how to test relays and such. it 's under more service repairs. If yu can make a jumper wiyou can discnnect the relay and jmp it to see if the fan works or not. I forget which relay is which but i think the fan relay is on the driver's side. Your fan relay could be on the firewall as well, like i said i forget.

okay, so i didnt have a check engine light at all. But i put the key in 'run' and jump the a + b on the aldl.... and presto! the fan comes on. no trouble codes, no flashing check engine light. so i fugure i can just drive around with the aldl jumped and that solves my problem, but unfortunately, as soon as i start the car, the fan stops. so now i know the fan works, and the wiring works. i couldnt find my meter but bought a new one and the switches dont seem to be getting power.

when you jump a&b on aldl and turn the key on that is how you get eh codes from teh computer check your computer ground and all the grounds on the car, like eng/batt batt/body. YOu have ot be getting a bad ground.