AC/heater and defrosters not blowing air out vents

Hello,

The first thing you must look for is to make sure the HVAC system is getting vacuum. Please inspect the vacuum lines from the engine to the firewall which feed the HVAC.

Here is a guide to help you see what I am talking about:

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

Please let us know what happens.

Cheers, Ken

I checked all the vacuum lines and they seem to be okay. But my HVAC vacuum reservoir is not getting any vacuum and the vacuum line is not cracked or broken. I disconnected the line to see if any air would release and got nothing coming out.
I than reconnected the line to the canister and the inlet port broke off. Also, the defroster is not blowing much air out of the dash like it should to defog the windshields. When I use to press the control defroster button the air use to be full blast to defog the windshields. I am thinking the canister is the reason because no air is even coming out the instrument vents either.

Yes, the system must have vacuum here is a diagram so you can see what happened (below).

All the vacuum lines are good under the hood. I just replaced some of the tubing on the egr harness. But the cruise control vacuum tank broke on me when I was disconnecting one of the vacuum lines to check if it still worked. Someone told me I would need to replace the Electric Vacuum Solenoid that works all the actuators. Would this fix my issue with getting no air out of the vents? Also would my defroster speed get stronger to clear the windshields?

Number 15 is what he told me to look at.

I remember a vacuum rotary valve on the rear of the control head that falls apart on these cars. Can you confirm you have vacuum at the control head?

I do not think I do. I have a vacuum control solenoid that connects to the passenger side blend door. I think that is the bad part because it is not opening the door on the passenger side when the blower motor goes on to put air out of the vents.

No vacuum to the control head is the issue. Find the broken line and it should be fixed.

There is a vacuum line that connects to the control head? Are you referring to the A/C heater control module in the instrument panel?

If no broken line at the control head could it be the control head it self? I heard they go bad sometimes.

I did check the lines and nothing broken near the control head. Only thing I found is the vacuum reservoir that broke. The line is not connected to that right now.

I want to know if the control head is getting vacuum and the vacuum reservoir needs to work and be connected. Can you take a picture and upload it here so I can see what you are talking about with the reservoir?

The control head is getting vacuum and the vacuum reservoir is connected. I already replaced the vacuum reservoir anyhow because I cracked it by mistake where the vacuum line connects to on the vacuum reservoir. I also checked all actuators for vacuum between 15 psi to 25 psi. It holds good vacuum in all actuators like it should. I also checked the vacuum solenoid box and heater HVAC blend door actuator and the metal pintle still moves each direction when temperatures are adjusted on the control head. Everything I know of that holds vacuum still holds vacuum. The only place that I can feel air is blowing out is near the blower motor blend door and the evaporator core duct cover.

Can you supply vacuum to each one of the blend door to see if there are any changes? It sounds like the door its self might have broken inside the heater plenum.

One thing I did notice was two of the HVAC vacuum panel mode actuators drop vacuum slowly when I was testing them. It is supposed to stay steady and it just begins to drop slowly. Also, the electronic HVAC blend door actuator barley moves and it connects to one of the doors. That actuator looks like it is connected to the passenger side blend door and it works the metal socket and spins each direction when cold/hot temperature is applied from the AC/heater controller.
The door should than open but it does not.

Mode actuators will drop vacuum slowly which is normal. It sounds like the main controller is out. If you can move the door by hand and they seem to work and the unit has vacuum power and ground.

If you are referring to the main controller on the instrument panel that is still working fine. I also tried replacing with a new one but did not fix anything. Please let me know what main controller you are referring to? I am thinking it is the actuator blend door that controls the temperature for AC and heat. Someone told me that had the same issue I am having when their vents are stuck in defrost mode. They said replacing the actuator blend door fixed the problem.

Yes, that could fix it. Here is another diagram I found for you.

Ken, I had no luck with that part either. I am thinking it is something really serious now. I hope one of the doors is not broke. Because than does not that mean they have to remove the entire air duct door assembly?

Ken with your experience of knowledge being in the automotive industry for so many years. What if my cars entire HVAC unit is bad? And if they do not make the unit because it is an older car. How much would it cost to replace the unit parts and labor? Is it in the ball park of what a house unit would cost? This is frightening me.

Do not get bummed yet, remove the blend door motors/actuators and move the doors by hand to see if they work. I have seen the blend doors break loose inside but it is rare. Also, while the actuators are off start the car and see if you can get them to move.