E34 530i, Overheating w/ AC on

[azdakarm3]

Few days ago, I encountered a situation where the car would overheat, only when I had the A/C on. Temperature has been around 105+ lately so of course I went for the A/C, few seconds later I saw the needle at the 3/4 mark, so pulled over at a local in-n-out and opened the hood and turned off the car. After about 15 minutes later got back on the road and was fine, A/C was off. Then I tried the A/C again and immediately overheated again, didn't pull over this time, turned it off, and within a second went back to the 1/2 mark. What gives? Bad thermostat? Doubt it would have anything to do with the water pump, since it was just replaced around last March. Thanks for your time and help guys.

[Alan]

If its only overheating with the AC on, I'd check the Aux Fan first as that is supposed to come on with the AC to prevent exactly what is happening. Its unlikely to be a T-Stat as you'd probably have the car overheating with or without the AC on.

[323I Junkie]

Check the engien ground too.

true story, I had a case where a bad agauge ground would fuel level to change and temp to increase with the ac on

aside from that, it really does sound like an aux fan, but check your clutch fan too...if its relying ont he aux fan to keep it from overheating, when you turn the AC on, it may be too much, ran into that too

also, check the relay for the high speed fan. if the contacts are bad, the relay may be "turning the fan on" and instead its actually just switching it from the engine temperature control to AC and then doing nothing

ran into that too, on an older acura

[de45t]

aux fan relay, clutch, or fan itself.