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Discussion Starter · #1 ·
I have a 1999 Jeep Grand Cherokee 4.7 4x4

I am having problems with the radiator fan working, I did some research and found that it's the relay under the headlight. So yeah I replaced it and well after I did the fan would run no matter what so I had to take out the fuse when I stopped so my battery would't drain and after 2 days the relay broke again. I have no idea what's going on with it cause I can't sit for too long without the engine over heating but driving it stays below 210... Anyone help?

Premium Member
10,283 Posts
I looked at the FSM I have. Here is what it says on the electric fan for the 4.7


The PWM relay is used to control the speed of the

electric radiator cooling fan. It allows for multiple fan

speeds. This allows for improved fan noise and A/C

performance, better engine cooling, and additional

vehicle power.

PWM relay operation is controlled by the Powertrain

Control Module (PCM). To operate the PWM

relay, the PCM looks at inputs from:

Ç Engine coolant temperature

Ç Ambient temperature from the body controller

Ç Vehicle speed

Ç Transmission oil temperature

Ç A/C switch position (A/C request

I think you have a sensor malfunctioning on this so the module thinks it is either in air conditioning mode or hot. I really think the best thing is to have someone scan the vehicle for all codes. There are a number of things that throw codes on the WJ besides the engine.
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