I turned the a/c on in my 97 3.8l to clear the mist off of the windows. Now, no matter what position the heater/ac/vent switch is in, I get defrost up to the winshield. I can control the temp and fan speed fine but not the a/c. As I said, it is stuck on a/c in the defrost position.

What type of control does the center dash switch use? Vacuum? Any troubleshooting ideas?

 

I would start by looking under your dash and looking for the fuse to the heater switch. I would pull that first and then to see if it's blown, and could be blown in the on position. If that doesn't work..i would get a technical manual...if you don't have one they sell them at pep boys for like 15 dollars....It's better to see if it's something you can fix then go spend money having someone else do it.

 

What year Mustang? Is the A/C actually on or are the vents just stuck in one position? If it's just the vents, it could be the cable or vacuum line that controls the position of the vents got disconnected. If the A/C is also staying on then take a look at the A/C cutoff switch near the evaporator in the engine compartment.

 

My original post says it all - 97 Mustang w/ 3.8l engine. Yes, the a/c is stuck on and is blowing from the upper vent for the defroster. The a/c isn't acting as if it is really charged well because it took a while to clear my windshield of condensation. But that is difficult to really tell since it was about 40 degrees outside.

Can you elaborate on the control from the a/c/vent/heat switch on the dash? Is it vacuum operated or cable controlled? And what does the a/c cutoff switch look like? I am generally ok with a/c components but do not know what this looks like.

 

OK, checked out the system and the a/c is low but that isn't the problem. The system is stuck so that the air only blows out of the defroster vents. So it looks like I am going to tear the dash apart and see what the culprit is.

Can anyone who has been inside the dash tell me what lies behind the switch? Is the system controlled by a vacuum switch or by a cable?

Gary
97 3.8L

 

I had a 97 CV that done the same thing. Vacuum leak. Start your car ,roll down your windows, take a propane torch (do not light) and slowly run the gas along the lines until the motor idles up. The line routing is prob different for you and I would start by taking a light and looking under the passenger side for the lines. They were easy to get to for me. It could also be the actuator or the actuator linkage so be sure to check those also.