cooling fans not working on Grand Prix

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cooling fans not working on Grand Prix

Unread post by chadder9 » Thu Jan 10, 2013 4:56 pm

ok i have a 2003 pontiac grand prix that neither cooling fans will work. even when i turn the ac on i cant get them to work. i have replaced the coolant temp sensor, thermostat and blead the system. when i jump the relay one comes on. also if i command the high fan control with the scan tool they work. im completly stumped.

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Re: cooling fans not working

Unread post by ProTech » Thu Jan 10, 2013 7:28 pm

Since you can command the fan on hi, or jump one of the relays, that at least tells you that the fans are functional and it isn't a motor problem. I would first start by checking all three fan relays that are located in the underhood fuse block. You could have one bad relay that is taking the whole system down. Also, there are two different fuses for the cooling fans, also located in the underhood fuse block. Check to make sure neither of those is blown.

If all of that checks out, I'd lean towards a PCM problem where it isn't turning them on when it should. Since you can command them on, I would also assume that the wiring is good. One thing you can check, if you have a scanner where you can watch the data stream, is see if once the car reaches operating temperature, see if the PCM is getting a signal to turn on the fans....even when you turn on the A/C you can see this as well.

I'd be sure and check that the PCM can actually see the temp from the temp sensor, too.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

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