I have a 1999 grand cherokee 4.0 .I have had the fan clutch relay replaced 3 times. Every time I bring it to the shop thats what they fix, they havent looked in to why it keeps going. If I leave it plugged in it just stays on even when the car is off. so I have to leave it unplugged or the battery will die . Which is fine now because its winter now, unless I leave it idleing then it will over heat. I had to have the head gasket replaced because I over heated when I was stuck in traffic a few months ago. So this has allready cost me a pritty penny and its still not fixed. Any help would be much appreaciated.

 

Are you taking it to a Jeep dealer, or an independant repair shop?

 

A private shop

 

sounds like you need to find a new shop that knows how to diagnose problems

 

1) If you note your temperature climbing, roll down the windows and turn the heater on full! That will help cool your engine...

2) There's no "fan clutch relay" - the thermal fan clutch is a mechanical device (temperature-variable viscous fluid coupling,) while the fan relay is for the auxiliary electric fan (you probably have two fans.)

The "fan relay" is tripped in one of two cases:
- The ECU sends out an "AC REQ" (Air Conditioning REQuest) signal to the relay, to accommodate the additional thermal load of the aircon system.
- The ECU senses the coolant temperature being above a threshhold value (~220-225*F for the 6-242) and tries to cool the engine down.

What are your symptoms? If it's just the fan staying on with the vehicle off, you have a wiring fault that keeps the relay coil energised. The relay doesn't want replacing, the wiring wants checking - and you're going to want a decent set of wiring diagrams to do the job (so you know what you're looking at.) If you're a neophyte at electric work, I'd suggest help as well - wiring faults tend to be fairly obvious on a visual inspection (burned bits, exposed copper, ...) but you'll want to make sure you're looking at the correct wiring - which is where you'll want to make sure you - or someone there - knows how to read wiring diagrams properly. It's not difficult, it just takes a bit of practise...