A/C - Defrost - Vacuum - what to check next

[davem]

I've read several posts about how a vaccum leak will cause the a/c to blow through the defrost vents. Under load, such as driving up hill/heavy accelleration, my AC will blow through the defrost vents.

A repair shop examined the vacuum lines under the hood, including to the cannister/ball, and thought they looked OK. Next they want $50 to run a 'smoke test' to look for a small leak somewhere. They also want to check the exhaust for a 'back pressure' issue, somehow affecting vacuum.

Is there anything else I can check myself ? Some unit under the dash/near glove box ?

Its a 2001 Explorer XLT, V-6, with 77K miles.

Runs fine, AC is good under normal load, and no engine codes.

Any help is appreciated.

Thanks.

Dave

 

[Turdle]

Could be a leak in the control switch--

 

[davem]

where is the control switch ?

Where is the control switch ? What does it look like ? How do I 'test' it ?

Dave

 

[Turdle]

Where is the control switch ? What does it look like ? How do I 'test' it ?

Dave

the thingy you turn to adjust the function--right below the radio silly

 

[BrooklynBay]

The plastic vacuum lines usually break right where they meet the rubber attachment which connects to a servo piston.

 

[davem]

where is the servo piston ?

where is the servo piston(s) ?

(Sorry, need a lot of help)