'97 F150 vacuum problem?

[CaptainFreon]

Hello
My pickup started having climate control problems. The dampers would modulate to defrost when engine loaded, then back to the setting when coasting. In time they just stay in defrost position. Now, the heat comes on and off by itself, even though calling for A/C. I can see condensate dripping out. I checked the refrigerant pressure, and they seem pretty close to parameters I read about here. I do commercial refrigeration, heating and A/C.

The 4 wheel drive partly engages and makes noise and sort of locks up, it took some gas peddle and brake to get it to fully disengage.

Is there a connection with the two issues?

Thank you for your time.

 

[CT8]

Sounds like it is a possibility.

 

[Charlie1935]

I would start by checking vacuum lines for cracks or a broken one.

 

[Chris142]

Originally Posted By: Charlie1935
I would start by checking vacuum lines for cracks or a broken one.
Theres a vacuun thing up in the passenger fender that often gets damaged. that or a check valve isnt working right.

 

[Rand]

when there is a lack of vacuum it will default to defrost.. so obviously the engine is still making vacuum.. you have a leak somewhere(or check valve)

 

[sleddriver]

I recently fixed a neighbors F150 with a vac leak. There is a thin, rigid white hose, in the engine compartment, on the passenger side, up near the firewall, that exits from a wiring loom. This hose bends around and connects to a vac motor controlling the fresh air/recirc door. His was in tatters.

Be sure to verify this motor functions when engaging MAC A/C.

 

[CaptainFreon]

Thanks everyone.