Help! 96 Corvette blend door not working properly

[96Corvette]

I have a 96 Corvette and the blend door moves from full hot to full cold on its own. There are no diagnostic codes stored, during the replacement of parts it did show 01 and 02 at times, currently there are none. Here is what I have replaced (in this order) inside temp sensor (used), actuator motor (used) (it did have a broken drive gear), programer (used) and control head (rebuilt). Nothing seems to have changed, you can watch the blend door move from hot to cold every few seconds just as it did prior to any parts being changed. The only glimmer of hope came when I replaced the inside temp sensor, the door did stop at mid point. The door shook from side to side so I checked the actuator and found a broken gear. From that point on it has continued to move on its own. Everything else seems to function properly with the exception that on auto, at full cold the air comes out the floor vents. On manual the vents all work as they should. Any help would be appreciated, I have lots of time and money invested.

 

[2VettesMike]

You probably have done this but just in case try pulling the HVAC fuse, small panel, on RH end of dash for a minute or so and plug it back in. Also could take the hardline approach and remove battery cable for the same time.

What this does, in my experience, is reset the HVAC by allowing the blend door to cycle to the stops. Sometimes it just loses it's mind.

Good Luck,

Mike

 

[96Corvette]

Thanks for the advice, but I had the battery unhooked each time I did any work.

 

[John Robinson]

You don't mention checking the vacuum. Here is a check valve that is famous for breaking the connectors off.



One vacuum line goes to the cruise and the other goes to the ac/heater controls.

 

[96Corvette]

On the 96 blend door it is operated by an electric actuator, but I checked the vacuum since I was there and it was "OK". Thanks for the advice. Everything seems to function, with the exception of the blend door.