Very unusual problem with a 1998 gt . My car was runninig hot and i pulled over and sure enough my radiator fans were not coming on. I replaced the relay to fan # 1 and same problem still accured. Next I checked the engine coolant temperature sensor located on the lower portion of radiator and when the ignition is on and the sensor is unplugged the fans come on. I then replaced the coolant temperature sensor
and the same thing happened. If sensor is plugged in the fans will not come on but if it is left unplugged the fans run constantly as long as the ignition is on. Does anyone know where the problem might be. Also does anyone know if it is fan #1 fan #2 or fan #3 relay that controls the radiator fans. Tahnks for the time and help it is greatly appreciated

can you try swapping relays?

I had the same problem. but one day when the temp was high i put a multimeter to the fan and read 14v so i was like **** the fans dead. and after a while i was doing something else under the hood like 2 weeks later.. and the fan started spinning like evrthing thing was ok...WTF...

how does a reading of 14V across the fans leads mean its dead? it means that its dropping all 14V that the alternator is supplying it, which is what it should be doing since its the only load on that circuit. if it showed like 9 volts across the leads when it was running then theres an issue in the circuit.


or do you mean that the engine was hot, fan wasnt moving, AND it was dropping all 14V?

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13 - 14v is normal with the car on, as that's what your alternator is putting out.

Manual swich and you ready to go. haha..... I did that and it works great, but I did not fix it. I just did it easy way. Do not take example from me....

you might try testing the relays, its pretty easy. all you need is
some wire
some crimp on female spades
a light bulb
a power supply

supply power to terminals 85 and 86 and with the light bulb hooked to terminal 87 and ground to terminal 30 then power attached to the free end of the bulb it should light. alternatly you could put the relay on the power side of the circuit instead of the ground side.

http://www.bcae1.com/relays.htm

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ya i know

i was reading 14v going to the fan but ..it wasn't moving

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ya that fan is probably on its way out. if you spin it by hand backwards does it make a clicking noise? also it should spin pretty freely in either direction. you could pull the fan blade and put a few drops of heavey weight oil at either end of the shaft as a temporary fix if you cant afford a new one now.

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The circuit is working properly then. Its actually more like a switch then a sensor, providing a ground to the relay which keeps the fan OFF. Once the temps go beyond a set limit, the sensor brakes the ground connection, turning the fan on. Its kinda backwars to the way you'd normally hook up a relay, but its designed so that if something fails the fans stay on. So the sensor may be bad - you can check it using a little hot water and a continuity tester.

Since the fans come on when the sensor is unplugged, you know the fan itself if fine. It also rules out the relay.

So if the fan isn't turning on, and tif he sensor in the radiator is good and thinks the water is not hot, perhaps the thermostat is stock closed and not allowing the cold water from the radiator into the motor? Or perhaps a clog somewhere, keeping the water from circulating.

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Was it the right (US drivers side) or left fan? The drivers side fan is the AC Condensor fan, which always has power and gets it ground from the relays.

could be a sensor????

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im not sure how he checked power but i was under the impression that he just backprobed the connector to the fan. in that case without a ground you wouldnt read anything since the voltage wasnt flowing to anywhere.

think of the wires as a hose and the meter as a flow rate measuring device. put you finger over the end of the hose and theres no flow so theres nothing on the meter.

Well, if he was messuring 14V across the fan then it would be the fan. If he was checking between a ground and the lead wire, then its a different story.

i used a multimeter. put it on both of the wires going to the fan.