auxiliary fan troubles

after much research, I'm still baffled. 88 4.0, peugot, minor overheating problems led me to find out why, I discovered my aux fan is not turning. multimeter shows 13 volts at the oem plug to the fan, bench test shows the fan does work at least by jumping it against a battery charger. what could the problem be?

Does it come on when you turn the A/C on? Checked the fan relay?

Johnnie Walker said:

Does it come on when you turn the A/C on? Checked the fan relay?

Click to expand...

There is a aux fan switch/sensor in the radiator, test it.

doesn't come on with a/c, but I do get the voltage at the plug when the a/c cycles...

no switch present in radiator, simply eliminated upon new radiator install, it did work after new radiator.

I just went through this exact problem with a guy on CC.

http://www.comancheclub.com/forums/viewtopic.php?f=2&t=24779

avnsteve said:

doesn't come on with a/c, but I do get the voltage at the plug when the a/c cycles...

no switch present in radiator, simply eliminated upon new radiator install, it did work after new radiator.

Click to expand...

if you've got 13V to the motor AND it functions correctly when jumped to good power and ground, you're chasing a bad ground. Try running an auxiliary ground wire from the fan to the battery and see if it works as expected then.

Ok, if you eliminated the aux fan switch from the radiator, and didn't relocate the switch, then your aux fan won't come on when the vehicle is running hot.

You have essentially disabled 1/2 of the aux fan's operating modes.

So, your aux fan is only going to operate in a/c mode.

Following testing information is from the FSM 88 and is posted here under the "fair use" rules:

"If electric cooling fan is inoperative when A/C compressor operates, start engine and turn A/C on. Disconnect fan relay connector. Fan relay is located on left inner fender panel.

Using a voltmeter, check for voltage at fan relay connector terminal No. 2. If voltmeter does not read battery voltage, replace fan diode assembly.

Disconnect fan relay connector. Fan relay is located on left inner fender panel. Using a jumper wire with an in-line 25-amp fuse, supply battery voltage to fan relay connector terminal No. 4.

If fan operates, motor is okay. Go to next step. If fan motor does not operate, check continuity between fan relay connector terminal No. 4 and body ground connections. If continuity exists, replace fan motor. If continuity does not exist, repair open and retest.

Disconnect fan relay connector. Turn ignition switch to the "RUN" position. Check continuity between fan relay connector terminal No. 5 and body ground connections. If continuity does not exist, repair open circuit. If continuity exists, go to next step.

Using a jumper wire with an in-line 25-amp fuse, jump across fan relay connector terminals No. 1 and No. 4. If fan motor operates, go to next step. If fan motor does not operate, repair fanrelay fuse link.

Check for battery voltage at fan relay connector terminal No. 2. Connect a jumper wire across radiator temperature switch connector. Radiator temperature switch is located on radiator outlet tank, above lower radiator hose. If fan does not operate, replace radiator temperature switch. If fan operates, go to next step.

Check for battery voltage at fan relay connector terminal No. 2. If battery voltage is not present, replace fan diode assembly."

Bad connection at the plug? I just currently had this exact same "Electrical bug" with a power door, after playing with the plug it worked. so i Butt-connected it.

thanks guys, I'll take joe peters' method to task tomorrow, I'm down with back troubles today, but Joe, your reply sounds very methodic and I appreciate the input. will post up when I get this done...

avnsteve said:

thanks guys, I'll take joe peters' method to task tomorrow, I'm down with back troubles today, but Joe, your reply sounds very methodic and I appreciate the input. will post up when I get this done...

Click to expand...

He's probably right. His Technical advice here is like an Ebay power seller. 99.46% satisfaction rate..

nw-xj-scott said:

He's probably right. His Technical advice here is like an Ebay power seller. 99.46% satisfaction rate..

Click to expand...

wow, you left a little bit on your chin there!

definitely was the diode. out of curiosity, what are the possible negative outcomes of removing the diode from that circuit? seems superfluous...

avnsteve said:

wow, you left a little bit on your chin there!

Click to expand...

:shocked:




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avnsteve said:

definitely was the diode. out of curiosity, what are the possible negative outcomes of removing the diode from that circuit? seems superfluous...

Click to expand...

anyone?

Feed back into the circuit causing damage.

Hit Radio Shack for a replacement.

A fan motor becomes an electrical generator when the blades spin on their own. There are lots of potential problems possible as a result of pushing current back through the harness. Safe bet is to replace it.