2001 - Max AC not working right under acceleration and a noise in new evaporator

[Ed Doucette]

Hello! I have two problems... some background:

2001 Explorer Sport, just had the evaporator replaced and the system recharged.

Problem 1: Noticed a few days ago that when in Max AC and the engine under load, the air flow shifts from the vents to the defrost vents only. I suspect a vacuum leak, but anyone have a idea as to where I should start? Also, this only happens in Max AC... in normal mode it seems to work fine.

Problem 2: Since the replacement, I hear a high pitch noise coming from the evaporator area when the AC compressor is running. It almost sounds like a fan motor whine, but since this only happens when refrigerant is running through the system, I have ruled out the fan motor. It continues and gradually fades when the compressor is turned off.

Thank you for any help or ideas you can offer!

 

[TheJackal]

Problem #1 could be a vacuum leak in the heater bypass valve.

 

[Ed Doucette]

Thank you for the help

Would a leak in the heater bypass valve cause only the problem in Max AC?

 

[Maniak]

It is a vacuum issue, but not with the heater control bypass valve. That valve just controls water to/from the heater core.

There are other threads on here about heat or a/c coming out of the defrost only. IIRC its a bad 1 way valve but you'll want to look around for that symptom.

EDIT: threads like this may help.. http://www.explorerforum.com/forums/showthread.php?t=251402&highlight=a/c+defrost

~Mark