99 dual zone HVAC problems

[fiddlersridge]

Hey all, got a 99 Gt with the dual digital(knobs with numbers on electric display) HVAc system that seems to work when it wants. I have checked for vacuum leaks under the hood but I still cant get the A/C to come on when I switch it on. Also, it has problems changing the direction of air(hot or cold) when I switch it. I will switch the direction and nothing happens, drive 10 min and it changes by itself. Any and all suggestions are welcome.

 

[FordMan77]

Does the A/C compressor engage when you turn it on? Might just be low on freon. There is a low pressure switch that will keep it from engaging if pressure is too low in the system (a leak somewhere).

Also, the air not changing direction from hot/cold sounds like a blend door motor. Does it change on the pass. side if you adjust the temp?

 

[Scottydoggs]

blend door actuators only control heat or cold air.

direction of flow is the vac pump linkage broke, vac pump broke, the vac line to the vac box broke or the vac box, broke, or the climate control its self broke.

 

[Frosty]

blend door actuators only control heat or cold air.

direction of flow is the vac pump linkage broke, vac pump broke, the vac line to the vac box broke or the vac box, broke, or the climate control its self broke.

Vac pump? Since when did grand prixs come with diesels and need vac pumps?

 

[Scottydoggs]

its more of a vacuum actuator i guess. it works off vac pressure. its in the dash and its what changes your air flow directions. ( you got 2) lots of plastic linkage that can break all on its own for no reason.

 

[97AutoXVette]

Scottydoggs is 100% correct on that. The vacuum line running off of the top of the blower to the passenger side of the engine bay next to the large relay/fuse box supplies vacuum to the motors in the dash to change direction of the air based on operator selection in the cabin.