2nd Gen Non-Engine/Transmission Another stuck on defrost question

[GHerrmann]

I did a search on stuck on defrost, checked to see if 4 wheel drive worked and it does. When in FWD all heater functions work, take it out of FWD and its back to defrost only. This must be a vaccum problem. I'm hoping someone can pin down a place to check the vaccum line, I'm disabled and climbing all over the truck will be quite difficult and trash me for the day.

 

[JR]

Have a look at the small lines along the firewall.

These lines need to be attached and free of cracks/holes.
This pic is just to the left of the master cylinder

 

[Ram4Sam]

Have a look at the small lines along the firewall.
View attachment 85203
These lines need to be attached and free of cracks/holes.
This pic is just to the left of the master cylinder

That is where mine was leaking... ... .

Sam

 

[Fireman Dave]

Mine was broken off going into the passenger side firewall behind the heater core.

 

[Bob4x4]

The vacuum motor that controls that door is just to the right of the accelerator pedal. You can verify vacuum right there

 

[Bill Lins]

Mine was broken off going into the passenger side firewall behind the heater core.

Same with mine.