I'm having a problem with my control selector. For some reason I only get defrost. It will not come out of the vent or the floor. The fan is working fine. Any suggestions would be greatly appreciated.

 

The system defaults to defrost if there is no vacuum supply.

There is a check valve near the brake booster. Usually it fails "open" and the mode doors change position when you accelerate but it may have clogged.

If you have cruise and it works, the valve isn't clogged.

If you can carefully pull the vacuum connector off the controller you can also find out if you are getting vacuum. Those hard plastic lines are very brittle and may have broken.

 

My cruise works fine...Do you mean the vaccum plug in the back of the control selector inside of the truck?

 

Yes, take it off and check for a strong vacuum supply.

 

Okay thanks for your help. If it doesn't have a strong vacuum then I have a vacuum leak some were? Is it possible that the valve by the brake booster is half clogged? I did mention that my cruise worked but it has been alittle slow to engage.

 

It could be partially blocked. At idle there should be a strong vacuum.

 

Thank you very much.

 

I check the check valve under the hood. I can only blow through one end...I cant blow through the other end? I also pulled the vacuum plug off from the back of the selector. There's 7 holes and I'm only getting a strong vacuum through 1 hole? Shouldn't it get vacuum to all of them?

 

There will only be a strong vacuum on one of them, the black one. That's the supply.

The control directs vacuum or vents the other lines depending upon your selection.

It sounds like it isn't a vacuum supply problem. It very well could be the control head. You can try to see if you can manually make the vents work but it isn't easy. To get just the panel vents you'd need to apply vacuum to all of the ports except for the dark green, that stays disconnected (vented).

It is unlikely that ALL of the actuators have failed. Do you have a vacuum gauge just to see what you actually have?

I'd suggest a junkyard for the control head. They can/do wear out and aren't cheap, if you can still get one.

 

Control head? I'm assuming the whole assembly that has the selector **** and the hot and cold ****?