Air conditioner (front only works if rear is turned on)

[tigman009]

I have a 2001 Expedition with manual A/C controls. The front A/c will blow only warm air with the A/C turned on to either regular or max settings. If I turn on the rear A/C the front will now have cold air. Any suggestions

 

[FordandPolaris]

does the rear have cold air as well, or warm air in back, cold up front?

 

[stamp11127]

I'm looking at the wiring diagram for a 99. Unless it changed for your year, the front "mode selector switch" is the one that sends the signal to the pcm to engage the compressor clutch. It also feeds power to the rear switch. They don't show any connection to the pcm from the rear a/c.
I'd check the front switch then proceed to the grounds behind the kick panels. This is wired with a few solid state boxes and a bunch of wires. I suggest getting a wiring diagram to make your life easier.

 

[tigman009]

The rear air conditioner blows really cold air.
1. turn on front A/C only and it gets warm air out the front vents
2. Turn on the rear air and the rear air is cold. Turn on the front air along with the rear air and the front is now cold.

 

[bojaz01]

it could be that a relay is stuck that controls airflow baffles between the front and the rear.........just my 2cents