AC is stuck on defrost.

I pulled out and replaced the switches and it didn’t fix it. I have no holes in the hose at all under the hood. (I smoke tested it). I changed the AC actuator and noticed that motor works for the heat/cool switch. I can’t figure out the problem.

Is there a motor similar that works the middle switch for defrost and AC? Maybe that motor is bad? I can’t figure it out. Any help would be great. Thanks

 

You smoked it, but if there is a pinhole, it might not show up. Do you hear any hissing from behind the climate controls or glovebox? If you have cruise, is it working? Check the vacuum canister behind the bumper as well. could be a blocked line, bad check valve, or a pinhole somewhere. https://www.cherokeeforum.com/f59/c-...efrost-195775/

Check any and all rubber connections, and replace if they appear cracked or dry rotted. You might have to squeeze them to find out.

 

The HVAC only blowing on defrost is a classic case of a vacuum leak. Look at the line coming out of the firewall near the heater core.

 

I checked the Vacume ball behind the bumper, no cracks or anything in that. The hose from that to the manifold has no holes either.

the small hose under the hood going into the fire wall doesn’t have any cracks either.

No I don’t hear any noises behind glove box.

I don’t have cruise.

thanks for answering.

 

When I turn that dial nothing happens, no noises or anything, it just continues to blow out of the defroster. Is there a fuse or anything for that dial? Maybe something with the electric to the dial? Is there another motor like the actuator i replaced ? I feel like I’ve tried everything lol

 

The entire system is vacuum controlled the no cruise control confirms it. Run the engine and pull the hose off the can in the bumper...it will not be sucking. There are several black/white discs in the lines...these are check valves one or more may be clogged. The lines for the door control system run in just inboard of the hoses for the heater core...hard to see comes off a t fitting

 

I pulled it off and the hose is sucking. Strong too. So the vacuum seems to be working ?

 

The vacume is sucking. I have no leak in the hose. Any other ideas why it’s only blowing out of defrost???

 

Ended up being the mode switch, just the dial was bad. NO VACUUM ISSUE AT ALL.

 

Common fault, but you wouldn't have believed it unless you checked it yourself.

 

Yup!

 

Just fixed that on my 96. The mode switch broke off (deteriorated plastic) so I got a junkyard dog and fixed it.