Cooling Fan Problem

[jfl330]

Related to a/c issue. Should either or both fans come on whenever the a/c is turned on? They do not now. I shorted the two pins in the pressure switch connector and still no fans.

Both fans DO come on when requested to because of engine temp, never goes over the half mark on the temp gauge. So the fans are good.

What can I check to see why the fan(s) do not come on with the a/c?

In case it is related, new compressor, dryer, orice tube, and expansion valve. Low side pressure >90 unless engine rpm's are over 2,000. Almost no cooling at idle.

Thanks,
Jon

[catvents]

Originally Posted by jfl330

Related to a/c issue. Should either or both fans come on whenever the a/c is turned on? They do not now. I shorted the two pins in the pressure switch connector and still no fans.

Both fans DO come on when requested to because of engine temp, never goes over the half mark on the temp gauge. So the fans are good.

What can I check to see why the fan(s) do not come on with the a/c?

In case it is related, new compressor, dryer, orice tube, and expansion valve. Low side pressure >90 unless engine rpm's are over 2,000. Almost no cooling at idle.

Thanks,
Jon

The following is for 2001 model but should apply to 2000. In the Battery junction box (fuses box & relay near the battery) 2 square relays are related to the fan. One is the H.speed fan relay and the other is the low speed fan relay. You can identified them with the help of the owner manual if you have it. While they look similar, the relay are different (pins configuration) I have got that problem just a week ago and I have replaced the low speed fan relay which you can get from a Ford dealership (inexpensive, $10 or a bit more) or maybe aftermarket. This has fixed the problem. And FYI, I suspect (while not sure) that if the low speed relay is defect, the high speed will not work.

[jfl330]

I checked lunch time, my car model/year does not have the relays in that location, 301 and 303 are empty. Apparently 1999-2000's were mixed.

There is supposedly a "Dual Auxiliary Relay Box" somewhere under the hood that will have these two relays. One speed is fine as they both run when PCM sense high coolant temp, so the other relay must be bad.

Jon

[12Ounce]

My '99 has the separate fan relays ... fastened to the inner wheel well ... kinda behind the regular fuse and relay box underhood.

[jfl330]

Found both relays in separate box attached to the driver side friewall. Pulled both relays, both good.

Next, have to find the dropping resistor for the low speed and see if it is good.

Any idea where the dropping is located?

Thanks!!!!

Jon

[Jeff Collision]

The cooling fans are controlled by the PCM (computer) grounding the fan relays from a signal from the, ECT (engine coolant temp ) sensor. The problem could be either a bad temp sensor and or the PCM is faulty and sending a faulty signal to the fan relays. I suggest you to check your fans relay well. It could be bad.

[jfl330]

Originally Posted by Jeff Collision

The cooling fans are controlled by the PCM (computer) grounding the fan relays from a signal from the, ECT (engine coolant temp ) sensor. The problem could be either a bad temp sensor and or the PCM is faulty and sending a faulty signal to the fan relays. I suggest you to check your fans relay well. It could be bad.

They work when the ECT says to come on but not when the A/C says to come on.

I have the two relays on my desk, they test good. Have to check the dropping resistor as this is apparently a known weak spot as the wires corrode and it becomes an open.

Should the dropping resistor prove to be good, I will short the low speed terminals in the relay box to simulate PCM request for fans. If this works, then time for a new pcm.

Thanks,

Jon

[12Ounce]

I would run the relays off of "engine run" before I would consider replacing the PCM. Lots of worms!

Relays can be difficult to test thouroughly. The relay coil may "lift" ... but the relay contacts may be slightly burned, placing a large resistance into the circuit. I would replace the relays with new before I spent much money on other items.

[jfl330]

Originally Posted by 12Ounce

I would run the relays off of "engine run" before I would consider replacing the PCM. Lots of worms!

Relays can be difficult to test thouroughly. The relay coil may "lift" ... but the relay contacts may be slightly burned, placing a large resistance into the circuit. I would replace the relays with new before I spent much money on other items.

Thanks for the good advice!

Jon

[azharj]

Dear jfl330
Did you solved your problem. or still having the problem. if not check on http://www.Sparky's-answers.com/ you may get some help. If u cannt open the link, search sparky's answer on Google and then open
Azharj

[jfl330]

Originally Posted by azharj

Dear jfl330
Did you solved your problem. or still having the problem. if not check on http://www.Sparky's-answers.com/ you may get some help. If u cannt open the link, search sparky's answer on Google and then open
Azharj

The problem is not electrical. It is pressure related, either high/low charge or a clogged system somewhere.

Thanks!

Jon