A/C, Defrost dash selector switch

[klwillis]

I have a 96' Ranger 4.0. The a/c fades out when going up a hill or pulling a trailer. I am unable to find a vaccum leak. Is it common for the selector switch for the a/c/ defrost and vent on the dash panel to go bad. I noticed all of the vaccum lines running to it. I am ready to pull my hair out. Give me a gas motor and I can fix it. When it comes to HVAC I stand and twittle my thumbs. Any help would be appreciated.

 

[Earl43P]

Find the vacuum reservoir.
It'll either be black plastic sphere or torpedo shape.
The torpedo shaped ones are usually atop the HVAC box (4 cyl).
The sphere may be under your air filter box on the fender liner.

Inspect those vacuum lines and reservoir for cracks.
The rubber fitting that goes into the sphere is a checkvalve. If it is bad, the reservoir won't store vacuum and any acceleration will deplete it and cause it to default to Defrost. I suspect that is your problem. Checkvalve might be available in the AP store HELP section. Pretty common problem on Fords.

 

[killj0y]

my a/c fades but only during wide open throttle, it will keep blowing but not cold air...maybe i have a leak too. I had this happen on another car i had but it would slow down and stop blowing altogether! It was a vacuum leak in the end gotta check these locations on my ranger

 

[Earl43P]

my a/c fades but only during wide open throttle, it will keep blowing but not cold air...maybe i have a leak too. I had this happen on another car i had but it would slow down and stop blowing altogether! It was a vacuum leak in the end gotta check these locations on my ranger

The WOT relay does that ^ on purpose, hence its name.