AC is working on Max AC only

[franklin2]

Ok so I went under the dash and found the vacuum actuator for the floor and the dash vents. I watched them carefully and the dash vent actuator only pulls back on MAX. Then when I switch to AC it slowly creeps closed. So it is slowly losing vacuum. I also took a look at the floor vent and found that it does not work at all. No hissing or sound of lost vacuum. It just does not move. I tried to move it by hand and it is not seized so I figure it might be something behind the switch panel or the switch panel itself.

Or I could be completely wrong and the system just does not have enough vacuum and it is something under the hood. I am just confused because it holds vacuum on MAX, just nothing else.

Keep at it. You are all around the problem now. You could get yourself a vacuum gauge and use it for testing.

You are correct about the hissing noise. You can apply vacuum and it moves the actuator, that makes sense. What you have to realize is when you move the control to the other way, it's going to stop the vacuum source to the actuator, but it also needs to vent the line going to the actuator to relieve the vacuum to it. If you tee your vacuum gauge into the actuator line(you could easily buy some line and a tee and make this) and you get vacuum when you move the lever, and then the vacuum never leaves, then you know the relief part of the control is not working.

 

[davidwatson833]

I am having a similar problem. When I turn on my AC in the morning it takes a while for the AC to switch from defrost to center vents. But only on MAX AC. If I change it to normal AC it will then switch back to defrost and no center vents. My truck is a 1998 2.5L Auto 2WD. I traced all of the vacuum lines in the engine bay and everything looks fine.

I'm the original poster on this. Can't help you on this. I haven't been able to fix my issue. The max ac is still working for me, but is a little flaky. Now that it is cooler, expect to check it again. From other things I've read, I think that Franklin is on the right path. I'll be inspecting these things as soon as I can.

 

[RedDragon777]

Well I feel dumb. I finished checking the vacuum reservoir and it checked out. Then I noticed that what I thought was a black line was actually the grey line. The previous owner fixed the line but way under the blower motor. So my lines were mixed up and the black line was on the heater bypass. Once I fixed that everything worked again.

On another note I found out why I had such a high idle. Someone messed with the screw on the throttle body and my idle was WAY too high. Now to find a new gauge cluster with RPMs so I can keep an eye on it.

 

[RobbieD]

Well I feel dumb.

Don't.

You fixed it, and did a great job figuring it out.

One of the "charms", of an old truck, is figuring out what all has happened to it in past.

 

[SenorNoob]

Previous owners do lots of weird things.

It's only slightly dumb if it was your previous work so you knew about it and just forgot. I do that all the time.

 

[RedDragon777]

Well my AC problems reared their ugly head again. I pulled out my guage cluster to change out the lights and i swapped out the ones on my AC controls for good measure.
Some reason I am having trouble with my AC again. When I switch to MAX the recirculation door does not open and I am not getting air through the vents.
When I switch to heat and try the vents and foot setting none of the actuators move. But for some reason that is beyond me if I set it to AC on cold it takes about 2 min and then I will get air coming out of the vents. But as soon as I switch to MAX from AC it shuts off the vents and goes back to dash vent.
It is 63°F outside but why won't my floor vents work on heat either?
Could my vacuum canister have a problem internally? Or god forbid my AC controls are on the fritz. I remember I had a problem with my father-in-laws 2011 ranger not charging because the dealer did not connect a plug behind the guage cluster. Could that affect the AC on a 1998?

 

[RedDragon777]

Well I did it. I changed the AC selector switch and BAM I have all of my functions back. So it was the switch after all