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Chris
Chris, Shop Foreman
Category: Jeep
Satisfied Customers: 3172
Experience:  Jeep Certified Master Tech
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I have a jeep grand Cherokee with the 4.0 and my cooling fan

Customer Question

I have a jeep grand Cherokee with the 4.0 and my cooling fan isn't working so I replaced the fan the high and low relay the 40 amp fuse and the thermostat and the thermostat sensor everything is getting power but its not sending power to the fan
JA: How many miles are on the car? Has the car been starting normally?
Customer: a little over 96 and the car starts fine no problems
JA: What year is your Grand Cherokee?
Customer: 2004
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I
replaced the fan the high and low relay and the thermostat switch
JA: Anything else you think the mechanic should know?
Customer: everything is getting power inside the fuse box but its not sending it to the fan
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Jeep Mechanic about your situation and then connect you two.
Customer: is it safe to run my own power and switch
Submitted: 5 months ago.
Category: Jeep
Expert:  Jared D replied 5 months ago.

Did you replace the pulse width modulated relay behind the bumper?

1. Check the Gray wire at the fan relay for B+.

2. Jump the Gray wire to the Dark Green wire. The fan should run.

3. Check the Black wire for a good ground.

4. Ground the Light Green wire to energize the relay and the fan should run.

5. If it does not run, the relay behind the bumper/grille is bad.

Customer: replied 5 months ago.
I don't have that relay ive checked its not there
Customer: replied 5 months ago.
I've changed my fan hi and low relay and thermostat switch everything is getting power in the fuse box just not sending power to the fan if you have a picture of the relay you're talking about that would be great
Expert:  Jared D replied 5 months ago.

You don't have this relay? It's a real bear to get to.

Expert:  Jared D replied 5 months ago.

It's number 1 in this diagram. It's on the passenger side just behind the bumper.

Customer: replied 5 months ago.
I don't have that relay I have the high and low relay with the 40amp fuse
Expert:  Jared D replied 5 months ago.

4.0l engine with the 8th digit of the vin is an S right?

Expert:  Jared D replied 5 months ago.

It's sometimes called the cooling fan control module. I've never seen one this year model without it, but I could be wrong.

Customer: replied 5 months ago.
the 8th digit is an s
Expert:  Jared D replied 5 months ago.

All of my reference material lists it as well:

Expert:  Jared D replied 5 months ago.

This control module is run by the PCM and works in conjunction with the other two relays.

I need to call it a night. I'll check back in with you tomorrow to see if you are able to track it down.

Customer: replied 5 months ago.
its under the passenger headlight correct if so I don't see it there I already cut the headlight housing out to make sure
Expert:  Jared D replied 5 months ago.

I don't think you would be able to see it after cutting the headlight housing out on the 2004. The vacuum reservoir would still be in the way.

Customer: replied 5 months ago.
only thing I'm seeing down there is my headlight plug nothing else is in that area
Customer: replied 5 months ago.
I removed the battery and battery holder box and I'm not seeing anything under there other than my cruise control piece and more wires one for the lights one for the fan one for the battery temp other than that nothing else is there what I will do is take a few pictures and send them to you if that's possible and see if you have seen this setup I was told it was a mid year model change whatever that is
Expert:  Jared D replied 5 months ago.

You won't be able to see it under the battery box. It will be directly underneath the headlight. The only thing I can this of is if someone relocated it.

Customer: replied 5 months ago.
That relay isnt on my jeep so im just gonna convert it into a mechanical fan and hope that works
Expert:  Jared D replied 5 months ago.

That is the strangest thing I've seen. Can you trace the wires from the fan connector back to wherever they go? Then from the high and low relay to wherever they go from there?

Customer: replied 5 months ago.
There are two wires one from the high and one from the low they both run from the relays to the plug everythimg in the box is working fine but the two relays arent pushing out power but you can hear them engage
Expert:  Jared D replied 5 months ago.

I've checked every manual that I have and asked all of my mechanics if they have every seen anything like that and we all agree that there has to be a fan control module somewhere. It can't operate on those two relays alone. The fact that there are two relays at all tells us that there must be a control module that tells when to kick in the high and when to kick in the low speed relays or the system wouldn't work.

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