Tacking the no floor heat. Passengers side the vacuum bulb controls vent and defrost. The switch/actuator is for the blend door. #20 is the bad door, correct.

 

Before you dig into the heart of the HVAC box, have you checked the condition of the under-hood vacuum hoses? Leaks there can cause some odd behavior.of the air distribution system.

 

Everything under the hood was replaced. The hack who owned it before the electrical tape was falling off.... 4 wheel drive was a 25% - 75% chance of engaging that fixed that! Coat hanger trick is next.

 

Check out this thread:

https://blazerforum.com/forum/2nd-ge...-airbox-99623/

 

Bonus shot! Thanks!

 

Hope it helps.

Be sure to report back what you figure out.

 

I'll be taking pictures! I knew I should have started this months ago, living in Wisconsin... It's getting cold. But, when you're friends have heated garages or lifts... I did both front fenders last year, got them off, ah, shouldn't there be wheel wells underneath... After I ordered the inner wells, all new body clips... Took over a month...