The far right dash vent does not blow as cold as the other vents. I run my a/c on max and highest blower speed. After the car cools off after 15 minutes or so, the air from that vent is colder. The temp difference is enough that I know it's a problem. I have verified that the a/c has the proper amount of refrigerant, and the a/c pressures seem ok, 40psi low, 200psi high, at idle in 95* ambient temp. I suspect it may be a blend door or problem inside the evaporator case. Anyone ever seen this before?

 

Ya I have seen this problem before, but not on an evo. I suspect its the blend door.

 

The first thing I would do is bring it to a shop that has an a/c machine, recover the refrigerant, pull a nice long vacuum on the system, and then refill it.

95% of the time this takes care of that concern.

 

If he had a leak in the system or refirigerant was low then he would not have gotten the pressures he stated. If all the other vents are blowing cold, then refrigerant isnt the issue. If a flapper door is staying open letting heated air through when you have the a/c on, then one or more vents will blow warmer than the others.

 

I am positive it is not a charge amount issue. I have already evacuated and recharged the system as well as pulled a vacuum before charging. I am a Tech at a Toyota dealer and have been for some years now(ASE, Toyota Expert Cert, etc). I have seen this happen on some of the older Avalons and Camrys and it was from low refrigerant. Since I have already verified that, I'm sure it's not the cause. I also noticed yesterday that it will also blow warmer on cold start. This also leads me away from a blend door since the heater core is not up to temp yet. My only guess would be possibly a partially restricted evaporator core or the compressor is going(pressures are ok, but not ideal).