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AC controls do not work properly

(1999 Ford Ranger)
in Franklin, TN on August 31, 2009
AC controls work properly on level ground but when I start up an incline the air is directed to Defrost. There is probably a leak in the lines or a bad diaphram control. Have check all under hood lines with vaccum gage. Put a hand pump with gauge on the line going through the fire wall. I can get it to pump up to about 10 lbs and hold. Looks like I have to go under the dash. Where and what should I check first? Thanks,

Bill P 53
Displaying 3 answers & 3 comments
Popular Answer
on August 31, 2009
Bret is right here's a blow up that includes the vacuum lines etc,51825&groupid=51827&subgroupid=2445&componentid=0&makeid=10&model=Ranger&year=1999&graphicID=MD98240&callout=21&catalogid=2&displayCatalogid=0 you can see all the vacuum operated doors etc hope this helps
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on August 31, 2009
The Diagram should help. Have been under the dash, through glove box. Pulled ALL lines loose, used hand vacuum pump with gauge, Unable to find anything that leaks.
Did the same (again) under the hood. Still fighting it. Almost has to be a leak as the "Blend Door" works until I go up an incline. Old guy, first car was a 34 Ford Cp, still tinkering. Hate to let something mechanical beat me.
Thanks to those that responded. IF or WHEN I fix it I will post the repair info.

Bill P.
on September 16, 2009
I FINALLY found the problem!! There is a vacuum reserve ball type canister hidden under the Right Front fender (at the very front) This is completely hidden by the splash shield. You will have to take out the WW washer tank, the air filter box and possible the cruise control box to get to it. Had a problem with a leak in the line going into it.

I kept checking ALL lines from the manifold intake to the vacuum connector block (6 lines going into it) mounted on the mixer box behind the glove box. Took me way too long to locate this problem. and isolate all the lines as to their function. IF you have this same problem, the BLACK line on this connector goes to the the tank mentioned above and into the intake manifold. There is a one way check ball in this tank/line.

Works GREAT now.

Thanks for the help and suggestions.

Bill P.
on September 16, 2009
OOPS. Did not think the first response was posted.
on August 31, 2009
Hi Bill,
You have a really good grasp on what is happening here. I'm looking for info about the vac. lines and cant find anything, but there should be a vacuum distributor behind the dash somewhere, and from there you can check each of the diaphragms individually. My guess is that one of them has a slow leak. Good Luck!
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on September 23, 2015
I checked all the vacuum lines and found broken end on the small grey line that goes into the mixer diaphram mounted to the heater hoses by the right side of valve cover. When I trimmed off the cracked end and inserted it back in the mixer diaphram, the AC still did not operate and the motor ran extremely rough. I disconnected it again so I could drive it to work next day. The defroster blows cool but no AC. What is the problem. Could the mixer diaphragm be bad??

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