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04 Forester X, MT
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1,039 Posts
Discussion Starter #1
I've noticed that my A/C seems to quit working if winding the car out. The fans are blowing but vent temperature increases very noticeably. Does anyone know if the system response is somehow limited - for example, does it cut off the compressor above a certain rpm? Has anyone else noticed this? A/C charge seems good and I've only got 90,000 miles. Guess I need to actually test it.

Driving "normal" i.e. not like a granny but not going above maybe 4,000 rpm I don't really notice this. The air seems plenty cold. I do notice air seeming to warm up going over maybe 5,000 rpm or more. This is noticeable with "spirited" taking off or when fully loaded and towing and passing cars (winding out!)

I've not noticed this behavior on other cars with low refrigerant levels. On those, cooling performance seemed to drop across-the-board and A/C vent temp was higher than it should be.
 

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Administrator
2004 Forester XT Premium 4EAT
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29,449 Posts
It's a "feature" - the A/C is designed to cut out when a higher load is put on the engine.
 

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04 Forester X, MT
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1,039 Posts
Discussion Starter #3
I wonder if there is any good way to defeat this "feature"? I would think folks liking this would be the exception? Like for racing or something?

I do have an X with the manual controls.
 

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1998 Forester
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213 Posts
Most racers remove the a/c system. The system robs power plus the weight of the system. This feature is programmed into the ecu.
 

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Registered
04 Forester X, MT
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1,039 Posts
Discussion Starter #5
So the ECU interrupts the A/C system signal internally? I would assume this would be based on some map of throttle position, rpm, and maybe other parameters? (Remember mine is 2004 that still has actual throttle cable).

Hmmm, I'll have to go back and look at wiring diagrams. It would be neat if you could have a "normal" and "bypass" switch for this A/C cut-out "feature".

If the signal were interrupted externally, this might be more open to modification.
 
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