AC blowing hot at idle but cold at higher rpm

I have a 2011 focus with AC blowing warm at idle but cold at higher rpm. I have tried a few things already and am stumped. So I checked low pressure and at idle it was bouncing around from 100 to 120psi and when rpms were increased to 2500 pressure went down to 35psi and was blowing cold air. The outside temp was around 90. I released pressure at idle until it was at 40psi at idle and was constantly blowing warm air at all rpms. When it was showing the high pressure at idle the compressor was working and fan was on. I checked the pressure this morning and it read 35psi. I added a small can of refrigerant back into the system this morning and it was brought up to about 45psi at idle and at the time the temp was around 75. It was blowing cold at all times. Now this afternoon the temp is back to 90 and pressure is reading 120 and blowing hot at idle again until rpms are increased then pressure is going down to around 40 and starts blowing cold again.

when the pressure is high like that on the low side, your compressor is likely not engaged.

You “releasing” refrigerant into the air (as it sounds like you have done,) is illegal and not a good for the environment.

The only advice I am comfortable giving you is to seek the help of a professional mechanic.


It’s much better to get a working knowledge of how the AC works before actually making any changes.If you need immediate results I also strongly recommend taking the problem to a professional.

I have decent knowledge of AC systems but haven’t come across an issue like this. I’m an engine mechanic and don’t deal with AC that often. I have seen high pressure readings like this on the low pressure line before but the compressor was not engaging. On this car the compressor is functioning. The high pressure readings are only occuring when the outside temp is 90 or higher. Now that the temperature is down in the mid 80’s the pressure as went back down a bit and the AC is working better at idle. I know the pressure changes with temperature change but I’ve never seen this drastic of a change.

You ever get a solution? My wife’s Impreza is doing a similar thjng

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The compressor was bad.

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What needs to be known with A/C problems is both the low and high side pressures at idle and at elevated RPMs. It may be a bad compressor on the Subaru or it might not be.

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The pressure reads 36 Lo 250 high when it is 85 outside and standard idle.

It reads 19/350 when it is at 2k rpm also at 85 outside