HVAC ISSUE

[Matt Vaughn]

I am completely stuck on what is going. 99 Yukon, the vent selection actuator by gas pedal. Here’s my problem, I’ve replaced the actuator, it will turn the blend door and seal the door so there isn’t any air blowing into your feet when the vent for face has been selected, than after a few times it will not turn all the way to seal for just face, it acts as though the face, feet mode is engaged, tons of air is getting by the blend door, I thought it was a bad actuator, maybe calibration came off or something so I bought another one. Same issue, works fine for a few days then will not seal the door all the way, I even replaced the door and the linkages thinking something was binding up. Still does it with a third actuator in. Will seal perfectly fine then after a few days, will not turn all they way. Therefore air is going to feet and face when face is selected. Idk what else to do this is so mind boggling. I need some help please lol. I should mention also that I will hear a click or a pop right before it does it, then it will never work right after.

 

[Schurkey]

What happens if you disconnect the battery for fifteen seconds, then re-connect and try the air door positions?

 

[Matt Vaughn]

What happens if you disconnect the battery for fifteen seconds, then re-connect and try the air door positions?

I actually haven’t tried that! What would that do? See if it’s a calibration issue with the actuator itself?

 

[Schurkey]

My understanding--and maybe I'm wrong--is that the controller "forgets" where the actuators/air doors are positioned when it loses power--so it cycles them to the ends of their travel to "re-calibrate" itself.

Try it, see what happens.

 

[GoToGuy]

There is a procedure in the service manual to enable the replacement to learn where " zero " is. In the HVAC section.

 

[Matt Vaughn]

There is a procedure in the service manual to enable the replacement to learn where " zero " is. In the HVAC section.

Do you happen to have a picture of that procedure? Unfortunately I don’t have the gm repair manual

 

[Erik the Awful]

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com