I had my blend door replaced a year ago, because the air was stuck on just defrost mode.

Now my heat /air is stuck on every vent? If i put the hvac controls on just feet it still blows out the face vents. It always blows out the face and feet vents no matter were i put the selection on the hvac controls.

any idea? suggestions?

OH, and my defrost mode still works fine tho... it turns off and on when in defrost. It must be two separate lines that feed the controllers?

 

There's three vacuum operated doors, two of which deal with defrost.

It could be the control itself. It applies/vents vacuum to the various actuators.

Try this, with the truck NOT running, move the control between the various positions until you don't hear them moving, it should only take a few times. Then, with the truck still off but the key on, put it on defrost. Turn the fan on high. You should only feel air coming out the defrost.

What this does is simulate selecting defrost. When in defrost it vents the vacuum to all (except the recirc) door. By not running the truck and cycling the control it should go only to defrost by default. No air should come from the vents. If it does, it's likely an actuator. If it doesn't, it's probably the control.

Hope it helps.

 

ok so,with the truck NOT running and the ignition OFF, move the controls between the positions...(face ,floor both etc.)
Then with ignition switch ON but truck NOT running put on defrost, turn fan on high.
If air comes out of the vents its likely a bad actuator (which one?) If air does NOT come out the face vents and only defrost its the controller? Is there any way to test the controller separately? Are they known to fail?
just wanna make sure im reading this properly
thanks for you help!

 

The controller itself is really nothing more than a valve. It directs vacuum or vents it to the various actuators. Be glad you don't have a 2001+ with the electronic controls!

Yup, you read it properly. If you've ever had a bad vacuum check valve on the HVAC system and went up a steep hill, your air would shift to just the defrost vents due to loss of vacuum. You're just simulating that.

You can test it. Download a copy of the FSM from here:

https://dodgeforum.com/forum/2nd-gen...-download.html

It's on chapter 24 page 54. 24-54. It'll tell you what oorts should have vacuum and what shouldn't for each position.

If it is an actuator, it's likely the panel/defrost actuator. since you say it comes out of the vents all the time. The other two actuator are the floor/defrost actuator and the recirc actuator. The blend door you speak of controls temperature and is cable operated.

Look under the dash, you can see some of the actuators. Maybe something is jamming them, a hose is off, or a linkage came off that you can reach.

If it is the control, try a boneyard.

Good luck.

 

My problem is my AC almost same thing but my fix is flipping the controller back a forth fast a few times seams to fix the doors not closing all the way it’s like slamming the doors in the vents it works for me.

If you don’t hear the doors slamming you have a problem either in the vacuum lines or controller.

The car must be running for vacuum to work and to try the flipping I think.

 

To try the flipping you need vacuum, yes. A vacuum pump is a handy tool for diagnosing this.

In this case though, we're trying to simulate no vacuum, normal ambient pressure. When there is no vacuum then the vent panel doors should be closed and no air coming out.

 

I found out that even not running the vent system has vacuum in the lines on my 1998 Dak I found this out pulling the vacuum line out in the engine compartment to see what would happen and it hissed quit well at me and you could hear the vent close in the cab I guess that’s a way to check if its working without any tools or gauges.

This is the one I pulled off if you look it has a one way valve to keep vacuum in the lines even if the car is not running.

 

Yes, it will hiss and there is a vacuum reservoir, a tank, under the cowl.

If you work the controls enough, you will bleed off the vacuum in it.

If that check valve is bad, if you go up a hill long enough the air will stop coming out the vents and out the defrost due to loss of vacuum.

 

A tank under there really how interesting why do you think my doors get out of whack at times crap inside the housing leaves so on.

My vents got wacked out after a shop removed the housing to replace the evap 5 years ago this shop didnt replace all my foam seals also causing my vents to make a wistling sound if using fan on the top two speeds crappy shop want to shoot them.

 

It might be stuff in the plenum, or your control might be leaking. You did say you have to wiggle it sometimes.