Thank you to everyone in advance for your help on this one. I have a 99 4.0, no real problems with it so far - owned it for 3 months, but today I had to drive to Vegas, and in the crazy heat, driving 70 mph, after 3 hours, temp gauge came on. I shut off AC, and before I could pull off the freeway, temp gauge shut off. I kept the ac off until I got to town, turned AC back on, and gauge came on again after 2-3 miles. Gauge turned off again right after turning AC off. I stopped, no coolant/ steam boil over, but I let the engine cool for an hour before finishing trip sans AC. any ideas on what could be czusing it to overheat only when AC is on?

PS - Electric fan is ALWAYS on, if engine is on, fan is on, and AC fan kicks on when AC is on. I heard that if the fan continues to spin after you shut the engine off it is a signal of bad clutch - is that true for AC cooling fan as well?

Thanks!!!

 

do you mean temp light? the gauge is suppossed to be on at all times.... the Efan is supposed to run when A/C is and when the temp reaches 217° +/- , by the way efan is on the drivers side mechanical fan is on the pass side it will always turn when engine is running. Also if you only have the lights not gauges you should search gauge cluster swap there is a reason they are called "idiot lights" they are unreliable although the stock gauges arent the best but they are better the lights you can also get an aftermarket gauge instead of compltely swapping the cluster

 

The AC fan is electric and should come on when the compressor kicks in. If the mechanical fan turns freely once the engine is at normal temp then its bad, it should have resistance to it. My daughters Volvo had the same problem and after replacing almost every thing else I changed the fan clutch and no more problem.