Cooling Fan Relay Question....

My fans do not come on with the a/c on. I pulled both fan relays, jumped the contacts and both speeds work. I checked both relays on a bench and both were good. Even though I knew better, I put a new 5 blade (low speed) relay in, no difference.

Should the fans run on low or high speed with the a/c? Should the fans come on pretty right away after the compressor engages?

Looks like my pcm may be the problem since the fan circuits are good. Does a used pcm have to be programmed? Or can I just drop in the correct version?

Thanks,
Jon

I'd check for applicable trouble codes, first. Anything? Next, I'd have to check voltage and ground circuits, where the relay plugs in. The fans should come on with ac. A new pcm will have to be programmed. I can't comment on a used one.

For A/C operation, there are two fan speeds. The fan operates at high speed directly through the high speed fan relay. The fan operates at low speed through the low speed fan relay and a high power dropping resistor.

The fan will run at low speed, high speed, or not at all depending on the conditions. I don't recall the conditions required to make the fan operate at high speed, but low speed is the initial fan operation when the A/C is first turned on. The relay is closed when the speed is below ~50 mph, and open (fan off) above that speed.

I've had the low speed droping resistor fail by the wire connection corroding and falling off.

Dear jfl330 (http://www.automotiveforums.com/vbulletin/member.php?u=438346)
Please check on http://www.Sparky's-answers.com/ (http://www.sparky%27s-answers.com/) you may get some help. If u cannt open the link, search sparky's answer on Google and then open doht go programming or changing for computers.
Azharj

A common failure is the radiator fan LOW SPEED dropping resistor breaking.
There is a metal bumper behind the molded facia bumper on the front of the vehicle.
The dropping resistor is mounted on TOP of the metal bumper on the passenger side.
It has a ceramic body with 2 wires coming out of it.
This resistor will disable the LOW SPEED operation of the radiator fans when it breaks.
It will not have an impact upon the HIGH SPEED operation.

If you raise the hood....and look down just behind the passenger side headlight....you will be able to see the Low Speed Dropping Resistor mounted on top of the metal bumper.....it is mounted to the bumper with 1 small bolt.

http://rides.webshots.com/photo/2458774470011220610ybouky?vhost=rides

http://rides.webshots.com/photo/2792266060011220610xhpbfu

http://rides.webshots.com/photo/2087855050011220610aPcAin

http://rides.webshots.com/photo/2857386550011220610BKLwAI

Not only is it helpful for your A/C for the fans to work, it really helps out the cooling of your transmission fluid in stop and go traffic.

I'm sorry that the pictures don't just show up.....the Webshots website is having a problem with the links for loading anything bigger than a real small picture directly.