jeep58

My coolant fan stopped working, if I put power direct to it will work. Is this the fan relay if so then how do you test the relay?

dave1123

You don't. It's a pulse-modulated relay controlled by the PCM and requires a digital input. Here's where it is;

It's underneath the passenger's headlight support panel. If the fan runs when hot-wired, the relay must be replaced. I went to replace mine and someone had already cut the hole so it must have been done before. This is a 4.0, if you have the 4.7 it's probably in the same place.

jeep58

Thanks, Another can this be converted to a clutch fan, without changing water pump, it is the 4..0 engine.

dave1123

Yes, it can, but I wouldn't recommend relying on just a clutch fan. In hot weather sitting in traffic my electric fan kicks into high speed quite often.

jeep58

The truck over heated on the way home needle came close to red zone, the guy hotwired the fan so i could drive home, truck maintained just below 210 when driving with fan on, mechanic said fan was not blowing hard enough, seemed to be be blowing good to me. Can the fan be weak, never heard of it. Thanks for reply!

jeep58

I put a relay in and fan does come on however the fan now will not turn over by hand,my guess is this fan is toast.

jeep58

Ok got same oem fan from another 2000 jeep grand, but the wires from the fan side do not have the connector they are black and blue. The connector side uses two reds, which wire goes to which side of the connector or does it matter. The connector is part of the wiring harness that goes back to the relay. Thanks for any help!

dave1123

The fan motor is a permanent magnet motor and polarity is important. You'll need to check which wire is ground and which is power to make it run the right direction, as in blowing toward the motor. Then you'll have to start up the engine and let it heat up until you get power from the relay (about 210*F). That will show you which wire from the relay to connect to the power wire of the fan. Use a voltmeter and check both wires until you get power. After wiring it up, check to make sure it's running the right direction. I used crimp-on spade terminals on mine using a male for power and a female for ground. That way if I ever need to take it out, I will only be able to reconnect it the right way.

If the fan motor draws too much current, it will toast the relay. One of the reasons for drawing too many amps is bad bearings or lack of lubrication. Either way, I'd replace the fan as well. I see you are doing that. Good job.

When that fan kicks on high speed, it sounds like a small hurricane. The way mine works is it doesn't run until the engine reaches 210* Then it runs on high until the engine cools down to 195*, then it runs on low until you shut off the engine or it goes over 210* again. What the pulse modulation does is turn the power on and off rapidly to make the fan run at low speed.

I wouldn't put my faith in a clutch fan unless you run BOTH that and the electric one. Some guys with XJs and ZJs who run offroad do both, using junkyard units from some other car. A Ford Escort seems to be a favorite.

jeep58

Thanks for the information, I connected the fan to the battery and it ran good seemed fast, I then took a test light and ran the engine probed the terminal and saw which one would light up verified by turning the A/C on and off. I will do the crimp on spades for the connection like you said, Thank you!

dave1123

Atta boy! I just didn't think about using the A/C bypass to identify the power lead! Good Job!

You know, I went to my Pick&Pull for that harness connector and out of 9 WJs in the yard, not one had a radiator or fan in it. Most didn't even have an engine in it.