So I noticed the other day my aux fan is not turning on 98 xj 4.0. So I thought easy enough pull the pig tail on the coolant temperature sensor and if the fan clicks on the sensor must be bad. Sure enough pull the plug on the sensor and the fan clicks on. Replace the sensor and it still does not turn on when the it gets warmed up. So i take the fan out and wire it directly to the battery to see if maybe it was a fan issue. It ran perfectly with no issue. So i figured it must be a relay issue. I took the fan relay and switched it with the starter relay as a simple test and both worked fine. The weirdest is part is when I turn the ac on (has never worked) or the defrost the fan does not turn on .Any idea what could be the issue. I have tried the three major components the relay, the fan and the sensor. Any help would be greatly appreciated.

 

If the A/C isn't working, (ie the compressor doesn't click and engage) then the fan won't come on with it. The compressor kicking in is what signals the fan to come on. Also how warm is the engine getting? It doesn't come on unless the engine gets above normal operating temp.

 

Bump

 

The Aux. fan will not come on until the engine coolant temp reaches 213 deg.F.

 

IIRC, seems like the a/c clutch relay can be removed thus immobilizing the a/c clutch. The efan still turns on in any of the 5 vent selector positions that normally engage the compressor even when the clutch is immobilized.