2004 Subaru Outback 100K overheats when a/c runs

Hi – My engine starts to overheat (the thermostat creeps up towards the red) when I run the a/c. This started this summer. If I turn the a/c off, it settles back to normal. Mechanics said a/c pressure sensor was defective and caused a/c clutch to stay on all the time. so they replaced the a/c receiver dryer (whatever that is). didn’t fix it. they looked again and said a/c fans were cutting out and causing overheating. they replaced them. that didn’t fix it. now they’re proposing exploratory open heart surgery: opening up the engine. if it only happens when the a/c runs, seems extreme. thoughts?

I suspect you need to find another mechanic. The clutch staying energized all of the time should not cause overheating and the receiver/dryer is a filter for the A/C system.
It’s unknown to me why they replaced this unless there was a system pressure problem due to a clogged filter.
If you have a clogged filter on an '04 Subaru then there’s a serious issue with a compressor. The odds of that are very slim.

Are the radiator cooling fans running with the A/C on? They MUST run and this is something that you could check yourself. Just let the car idle with the A/C on, raise the hood, and note if they’re spinning away.

Does the engine overheat during city and highway driving both?

One thing you must do until this is sorted out is not use the A/C. Subaru engines are all aluminum construction and chronic overheating is not good on them.
Without knowing what the system pressures were, or are, I have no idea why the dryer was replaced or what’s really going on with the A/C.

I have to second ok4450’s assessment, especially about finding a new mechanic. What these characters have done makes no sense whatsoever. It seems to me that they are making weird guesses on your tab.

At this point though, you want to worry about whether or not the overheating has created a head gasket problem.

Thanks for your feedback. I did the following check: turned the engine on and let it idle. The ventilation system was off. The fans didn’t run. Turned the ventilation system on but left a/c off (so plain air was coming out). Fans still didn’t run. Turned the a/c on. The fans immediately turned on.

The overheating problem happens when I turn the a/c on during both highway and city driving. And does not ever happen when I leave the a/c off.

I have found the name of a well-recommended local mechanic on this website, so will give him a ring. Any other thoughts you might have are certainly welcome. Thanks again.

Possibly a weak water pump or partially clogged cooling sytem? Might be good enough to handle normal driving but not the extra burden of the a/c?? Just a thought.

With the fans running and overheating only happening with the A/C on, I’d have to think this would be caused by:
Sludged up radiator.
Bug clogged A/C condenser.
The system pressures are not correct and the high side is too high. Knowing the pressures at elevated RPMs might help to clear this part of it up anyway.