2000 Silverado LS, 5.3, Reg Cab.:

I'm really hoping someone has seen this air distribution system problem and can suggest a likely fix.

Heater and AC work fine all the time. The problem happens if any mode is selected that calls for "outside air" . When the outside air button is pushed, or 'defroster' is selected, a door under the dash activates and repeatedly bangs back and forth. If I press 'Recirculate' or leave defrost and go back to dash and feet air circulation it quits 'banging open and closed'.

I've taken the lower air distribution cover off and can tell the 'banger' is near the center-right of the dash. I really can't see anything at this point. I've removed, cleaned and reinstalled a number of the electrical connectors that are visible with cover off.

I have the factory manuals but can't find any similar symptoms.

I DON"T WANT TO DISASSEMBLE THE WHOLE DASH IF I DON"T HAVE TO.

Thanks for any help you can give!!

 

I would have to guess that one of two things is happening...either the fresh/recirc blend door actuator is malfunctioning, or the linkage from it to the door is disconnected/popped off track so to speak, or the door itself is somehow binding. Can you see the actuator arm moving back and forth? If you can access the actuator, I'd try removing it and seeing if the door moves freely by hand, if so, I'd say that there's a problem with the actuator.

 

Thanks for the info Bud. Actually, I can't see "anything" move with just the large bottom cover off. My problem is where to start 'disassembling' things to be able to see the problem area.

I'll get back into the ,manuals, and look for "connecting/removing blend door linkage"; and maybe that will get me in the game.

Thanks again for the response.

EDIT to add: It looks like I may be able to try your suggestion (remove act. motor-move by hand); but getting access to actually clean or replace the valve/door looks like bad doodoo in the manual.

 

There is a calibration process for the actuators. Each actuator has to learn its positions. This can only be done with a Tech 2 scan tool. Any dealer will have it and many independent shops too.

 

MrG: Ouch. The factory manuals didn't mention that in the sections I was looking at.

Thanks for the heads up.

Will it need that, if I remove the outside air actuator to test for movement of the door/valve, and then reinstall the actuator??

 

Well, I took the glove box out and can see the trouble-maker above the Glove Box on the passenger right side..

The outside air door seems to move freely and isn't clogged up with anything visible. It isn't even dirty---looks new.

The door goes to the 'inside' air postion smoothly---up and shut.

When it goes to 'outside' air, it moves smoothly, seals and then drops back about 1/2" or more and tries to reclose. It does this over and over until I switch to inside air where it moves up, seals the outside air opening and shuts off.

I can see the actuator/motor on the left side of the door. It has a shaft that drives the door sticking out the back side of the motor about 1/4" . The exposed end of the shaft has a slot in it like a large common screwdriver slot.

Has anyone seen this problem?

Is the Actuator 'slipping' on the shaft some way, Is it just a programming job, or a bad door motor?