Okay, lately my AC isn't blowing cold at all even though its full with freon. I've converted from R12 to the R134A freon and it was working fine until not too long ago. What could be causing the problem?

 

This is on a '91 Legacy AWD.

Are you sure it's properly charged? How are you testing the pressures and what are you getting for readings?

 

If it was overcharged the compressor won't come on. It's possible it was overcharged previously but ambient conditions kept it *just* under the limit. Now that conditions have changed maybe it's finally over that pressure limit for the pressure switch.

 

When you turn it on is the A/C compressor coming on at all? Can you see it engaging for a second when the A/C is turned on? And then does it - shut off, cycle on and off, stay on, or never click on at all?

Yes, the compressor engages when I turn on the AC, just no cold air coming out. I use a recharge kit with a pressure indicator to measure it. Can there be such thing as a bad compressor even if it's engaging fine?

Are you sure it's properly charged? How are you testing the pressures and what are you getting for readings?

 

If it was overcharged the compressor won't come on. It's possible it was overcharged previously but ambient conditions kept it *just* under the limit. Now that conditions have changed maybe it's finally over that pressure limit for the pressure switch.

 

When you turn it on is the A/C compressor coming on at all? Can you see it engaging for a second when the A/C is turned on? And then does it - shut off, cycle on and off, stay on, or never click on at all?

 

A friend of mine had the same issue. He though it was fine till I threw on the gages. Way over charged. The temps spiked up one day causing the pressure to increase in the A/c System and causing the high pressure limit switch to cut the compressor. I think you are right on the money Gary.

Yes, the compressor engages when I turn on the AC, just no cold air coming out. I use a recharge kit with a pressure indicator to measure it. Can there be such thing as a bad compressor even if it's engaging fine?

 

Yes. My 98 Outback did this until it finally siezed causing a cloud of belt smoke from under the hood. Internal failure can cause your issue.

I have seen compressors fail in any number of ways, but I have NEVER seen one fail in such a way that it continued to run without any strange noises (which would be INSTANTLY noticable to the driver) but without producing a cooling effect. Not saying it CAN'T happen, but it would be a REALLY strange mode of failure.

 

If the compressor engages and runs, then neither of the pressure switches is engaging. Which could indicate a proper charge. Or it could indicate that one or the other pressure switch is not functioning.

 

In the end, an AC system is a rather simple system. If there is refrigerant in the system and the compressor engages, then you should have cold air. If that doesn't happen, then the only way to diagnose it is to put a set of gages on it.