I have a 99 Buick Century with a 3.1 V6. I have checked the relays all three check good, I have checked the fuses they are all good. I have jumped the fans and they both work. I feel there is a thermostat controled swith that sends a signal when the fans need to come on but I cannot find it. can anyone tell me where it may be located?
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Re: Cooling Fans Not Working
Thermo sensor switch in cylinder head might be in thermostat housing or in the cyl head some place in that area look closely you will see it usually 2-3 wire plug it is brass with black plastic type plug on end good luck.John
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The cooling fan circuit receives power through fusible link F and the 10A engine/AC in line fuse. Input from the engine coolant temperature sensor is applied to the PCM which, in turn, closes the primary and pusher coolant fan relays to turn on the coolant fans.
A blown fuse usually results from a circiut overload or short. First check wiring from fans for any breaks, rips or tears in wiring. Next with the engine off and cooled down, see if the fans will spin freely if you spin it. If they don't spin then they have siezed and the circuit is getting too hot. If they do spin then it is likely you have a short in the wiring.
The ECM turns on the fans when the engine tempurature gets to around 210 degrees. You could have a bad coolant tempurature sensor, not telling the ECM that the engine is hot enough to turn on the fans. I would check to see if the fans come on when the A/C is turned on. Or there is a problem with the ECM. The ECM supplies a ground to the cooling fan relay to turn on the fans.
FIRST IS CHECK ENGINE LIGHT ON....YOU SHOULD BE ABLE TO UNPLUG THE ECT... ELECTRONIC COOLING TEMP SENSOR.....A TWO WIRE SENSOR THAT TELLS THE COMPUTER THE TEMP OF MOTOR....WHEN THE MOTOR TEMP GETS HIGH THE COMPUTER GROUNDS THE COOLING FAN RELAY TO TURN FANS ON..IF FANS DON'T RUN WITH SENSOR UNPLUGGED THE GET A SMALL PIECE OF WIRE AND FOR A SHORT TIME SHORT THE TWO WIRES ON THE PLUG FOR SENSOR...IF IT DOES COME ON REPLACE SENSOR IF IT DOES NOT COME ON SUSPECT COMPUTER...ONLY IF ALL FUSES ARE OK LET ME KNOW