My daughter has a 99 Cherokee sport. I have been chasing down electrical problems as of late and the most recent one has me stump ed. The ac is not working. The check engine light came on with a code that said cooling fan circuit. I found a schematic of the cooling circuit and after I verified all the fuses and relays were good . If I force the ac clutch relay by applying 12V across the coil everything works the way it should. So it appears I'm not getting the signal to energize. Where does that signal originate? I have heard the ECU can be the problem I want to rule out any other components before I spend $300 that may not fix it. HELP

 

Check the cooling fan relay. It's in the Power Distribution Center on the passenger side of the engine compartment & the lid should have a label.

 

The ac clutch relay is before the fan relay in the circuit. So when I energize the clutch relay it turns on the fan relay and fan.

 

Check your sensors for A/C? If it's too low on freon your sensors will not allow clutch to pull..or if your a/c system is full then your sensors might be bad

 

The fan relay also works independently of the A/C circuit, because the PCM also switches on the fan when temperature reaches 218 degrees. Whether your A/C is on or not. The PCM will throw that CEL if there is a problem with the fan relay circuit.

 

I have replaced the cooling fan relay early on because the "CHECK ENGINE" code said cooling fan circuit fault. Where is the pcm located and is there any schematics available? By the way, I put jumpers across the a/c sensors and that changed nothing. I'm not sure if that was the best way to check that sensor circuit. Thanks for the help. This is my first time using a forum like this.