Hello all,
My 2010 G37x is overheating only when AC is on. I was stuck in traffic in very hot weather when I noticed the needle hit H. Pulled over and parked underground and went into mall for a couple of hours. I checked for leaks, overflow and radiator levels and everything checked out. I did the self test and can hear the fans spinning. The next day, I drove the car again and it was scorching hot but did not turn AC on and the car did not overheat at all. I haven't flushed the radiator in years, could old antifreeze cause this? Any ideas?

Thank you.

 

The ac puts an additional load on the engine, so it seems a likely cause of overheating, especially when the coolant is old and may have reduced resistance to boiling and freezing. Old fluid also becomes acidic over time, which can also cause rust and scaling to build up in the radiator, minimizing its effectiveness.

 

What symptoms were you having to say your car was overheating? Was there any steam, bubbling from the overflow tube, higher than normal engine idle, or was it just the idiot gauge reading "H?"

When you ran the self-test, did you visually see that both fans were running at 50% and 100% duty. At 100% duty those fans should be roaring loud.

At the very least you should change your coolant/ flush your radiator, if nothing other than for proper vehicle maintenance. Also, make sure the exterior is clean/ free from dirt, bugs, other debris that can restrict airflow across the radiator/ condenser.

 

Was only the gauge at H with a burning smell,no steam. With test, can hear fans but no "roaring". In any case, the car is at the garage now and my regular mechanic just called and told me one of the fans is dead and the modulator is blown. He is checking for parts and will let me know soon.

Does anyone how much this will cost? A new fan, module and labor?

Thanks

 

I doubt it is the fan control module but anything is possible. The module, depending on where you/ your mechanic get parts, should run ≈$60-80. As for the fan, new from the dealer will run anywhere from $250-300- depending on if the right or left motor is shot. Labor is up to the mechanic and whatever his rates are.

When I did mine several years ago, it took me about a hour though I replaced the entire cooling shroud/ assembly as a whole. In your case, just to replace the module and motor should not take more than a hour or two.