Defrost/heating question on 1990 Chevrolet 1500 Pickup

I actuallu have a 1988 1500. I cannot get air flow from the heater or AC into the middle dash or wundshiled defroster. I have removed and tested the AC Actuator and the Temp Actuator and they are both working. The vent that I can see through the opening for the factory tape player is closed and I can't get it open. I have literally torn this dash apart and cannot figure out the problem.

3 answers 10 comments
I would subscribe to for your Chevy truck. here you can get all of the factory info with the HVAC diagrams, so you can trouble shoot which vacuum motor is not working or which door is jammed. It will cost $26.00 for a 1 year subscription for your vehicle's info. Best of Luck!

Actually, you often have to completely remove the dash from a vehicle to repair heating and ventilation problems because it is the only way to really access all the components. It makes HVAC a tough repair in most cases.
I did. Thanks. I got it for 12.95, but it didn't solve anything. All the actuators seem to be working. I have removed them, opened them up and saw the little motor spinning. There are some vents stuck in the closed position. The problem is I can't get to them.I have tried everything short of unbolting the dash from the truck. Chevy dealer was of no help. They just want to put me through the same routine they do to everybody. If they would let me talk to a mechanic (it's like trying to get in to see God) I could explain what I already know and sve him a lot of trouble. It could be the controls it might not even be machanical. Doesn't seem like there is a lot of interest in this board, if you know of a better one let me know. Thanks for your suggestion.
I'm having the same problem. was wondering if you ever got it fixed and if so how? rkatmont
i have a 1995 chevy truck, same problem, could it be the control unit
In order to really deal with the doors and motors in your Heating and A/C unit, you WILL have to pull the dash. Then you pull out the Heating and A/C plenum or box and you have to put it on a workbench and then test all the doors, motors etc. It is a very labor intensive job to do. The motors may spin but many times the little gears are stripped that actually open the doors and do the work, so be sure to check those. Alldata should explain how to remove the dash, but as far as Diagnosis goes for Heating and A/C, in most cases, that is up to the mechanic working on the vehicle.
Thanks. I guess there is no easy solution to this. Something must be stripped or jamed. I can't see much from underneath the dash as there isn't a lot of room to work. I don't recall seeing info on removing the dash in Alldata and my subscription has run out. I am not sure that I would go to that extreme anyway. I may have to adjust to it. Right now I live in Hawaii and never need to use the heat. I am selling the house here and we plan to move back to California. Its colder there and we will need the heat. I want to take the truck. It is in great shape and has only 74000 origional miles on it. This is the only real issue it has. Thanks for your interest.
ck vac hose going into fire wall from under hood
I don't belive that there are any vacume hoses associated with the heating system or vents. The vents are operated by small motors and they all work. I have removed each one and opened them up and watched them work. Something else a lever is stripped or the vent(s) are jammed. I just can't get in there and can't see anything from below. It may also be the controls. I have removed it and taken it apart as well but its all electronic. I can't tell visually if it is working and can't find another one to swap it out to se if that makes any difference. Thanks
I ended up tearing the whole dash out(big job) and found that the door to the vent and the housing were stuck together. after freeing them up and cleaning said parts it all works fine now.
Thanks. I may have time to do that, but I don't know where to start. I have tried to get in there by removing the glove box, stereo and spedometer cluster. I can't see how to get any deeper. Do you pull the dash out from the fire wall?
start by removing all the panels buy the steering wheel. unbolt the steering from the support, I didn't have to remove it by unbolting it it will move far enought to remove the rest of the dash. you have to remove all of the other panels to get at all of the screws and bolts to remove the rest of the dash. then you can see the door for the vent. unstick it and clean and lube with a dry lube check to see that it works. reinstall and you should be all set.
Are "all of the other panels' that you refer to in the second sentence, behind "the panels by the steering wheel"? And by "removing the dash" do you mean the whole thing that holds the speedo cluster, radio and glove box? That whole in my case, blue, vinyl covered thing that stretches from the drivers side to the passengers side, comes out?
there are panels all across the bottom and around the heater/radio and yes you have to remove the whole blue thing.