No rear heat

[SnowDrifter]

'05 Tahoe LT, auto climate control


Haven't used my rear heat since last winter. Went to use it the other day and found it not working

- Both rear heater core lines are warm
- Switching from overhead to feet-heat works

Just trying to figure out what my diagnostic tree here is. Control box? If so, how do I check? Blend door actuator? Again, how do I check? If the plastic bits are seized, what's the best approach to ensure they don't stick again in the future?

Just trying to get all my ducks in a row before I tear into it

 

[Z28TWITCH]

Had a Yukon do the same thing. Replaced the module in the back and fixed it.
P/N 15832319

 

[SnowDrifter]

What's the proper test to verify that the module is bad?

 

[Z28TWITCH]

That to be honest I cannot answer. I played around with a few things and that was the easiest/least time consuming to do. I guess a lot of tahoes and yukons have modules that are just crap right out of the box and it's a fairly common fix from what I understand.

 

[SnowDrifter]

So... This is sweet

Pulled it apart to start checking pinouts in accordance with the video listed below.. And it decides to miraculously work again. Little frustrating