# Radiator fans only come on when A/C is turned on



## jamesd3rd (Jun 10, 2004)

This was the only way I can get my radiator cooler when we had some very hot days recently. For some reason, they don't come one otherwise. Possible temp sensor problem or something else?


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## Asleep (Jan 19, 2003)

if youre not overheating, youre fine.
if you are overheating, then change out the coolant temp sensor. its only about 18 bucks at autozone.


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## jamesd3rd (Jun 10, 2004)

Asleep said:


> if youre not overheating, youre fine.
> if you are overheating, then change out the coolant temp sensor. its only about 18 bucks at autozone.


That's just the thing. I was watching the gauge climb as I was sitting in bumper-to-bumper morning traffic. It was barely 11:00 in the morning and it was already shaping up to be a hot one. Then I turn on the A/C, the fans immediately came on and the gauge gradually came down. Never mind the fact that the A/C doesn't work and I still had to drive with the windows down.

Hopefully it's just the temp sensor and not something else.


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## Asleep (Jan 19, 2003)

sounds like the temp sensor. have you had a decline in gas mileage lately?
that would definitely single it out.


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## Garage Battle (Feb 25, 2004)

sounds like a fan relay

check the relays for RAD FAN 1, RAD FAN 2, RAD FAN 3.

I would say to do this. Let the car run. When it starts showing its hot, turn the car off, switch the relays for the fans from one to the other and immediately start the car. If this is correct your fans should come right on. You could also goto advance, buy an extra relay and try it, but I think the switching between relays should be enough test.

btw both fans are 4 wires, 2 speed. each speed has its own ground and 12v. the 12v is switched by a relay. the relay is activated by a 'ground' pulse from the ECU.


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## Asleep (Jan 19, 2003)

the relays are activated by the temp sensor. proper troubleshooting will have you test the connections and then the sensor before you replace the relays which are simply on and off switches.


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