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Electric fan crapping out...


NAXJA Forum User
Johnstown PA
Ok guys, here's what I have.

It seems as though that my electric cooling fan runs slower and slower as engine/underhood temps go up.

For example, when I left work today, I started the Jeep and kicked the AC on; the fan roared on nearly full speed.(Not quite how it used to, but pretty close) When I got home (1/2 hour trip) and backed into the garage, I had the window down and I could barely hear the fan running. I popped the hood, and it seems to be running at only about half-speed.(and struggling to do so)

It's been doing this for a month or so. I just recently got the hunch that it might be related to temps. I parked right under the fan and left the hood open for everything to cool down. I went back out a couple hours later, started it up, kicked the AC on, it roared on.(Again, nearly full speed) I drove around for a little while, long enough for everything to get hot again, and sure enough it was running much slower than when I first started it.

I'm guessing that this is a sign that maybe the fan is starting to show it's age. I should also note that I switched the fan relay with another one... no change at all. So we can rule that out...

Any other ideas are welcome before I bite the bullet for a new fan...
If you do bite the bullet buy one from Quadratec.com. It was $80 cheaper than what my dealership quoted.
Check the voltage drop on both legs of the fan. For the uninitiated, this involves using both leads of a voltmeter on the same wire. So you'd go from the back of the relay on pin 87 with one lead and put the other on the fan side of the fan connector on the hot lead. Backprobe it so the circuit is still intact or your test means nothing. Of course, this is with the fan running.

Do the same test on the ground side as it also flows current, just as much as the positive side. If you find more than .5 volt showing up on your meter, you have a high resistance problem in either a wire, connector, or bad ground. If you have excessive voltage drop move around the circuit to pinpoint the trouble area.

If the voltage drop tests show less than .5 volt on positive and negative, you have a problem with the fan itself.
bustednutz said:
Quick question, did you ever replace the fan? I'm wondering because my 98 is doing the EXACT same thing. EXACT same symptoms.

Nah, I haven't replaced it yet. I was trying to figure out a way to test the power supply circuit. I hadn't even thought of a voltage drop test. I'll be doing that either today or tomorrow, so I'll be sure to post results....
I picked up a replacement motor for a later model XJ aux fan from Carquest and it works very well. I think it ran me about $76. I noticed a much stronger pull than the motor that it had when I bought it at Pick your Part.
This is similar to a problem I am having. When I first start up mine in the morning or at work(after sitting all day) The fan comes on. After it gets up to temp. it won't come on at all.

Where is the relay so I can check it? Also a couple times I've been able to start the fan by spinning it with a screw driver and it goes, but sometimes it just won't come on at all.
The fan is shot. When it gets too hot under the hood the motor becomes weak. I could also spin mine with a screwdriver and get it started, but it only moved slow.
So I just bought a new one from quadratec for 95.00. Going to install this afternoon or this weekend.