Intermittent A/C Problem- Help

[Gidg]

I just bought a 2000 7.3L Excursion. The first day I had it, the A/C worked great, blew strong and cold, all day. Stopping, starting, stopping, starting, no problems. On the second day I had it, I started it in the morning and the A/C was cold, but blowing out the defroster vents instead of the regular vents. I had not changed any of the knobs. The next day, when I started the car the A/C was blowing out the regular vents just fine. I have had the car for two weeks and this has happened about 4 times. Any ideas about where to start looking?

[cjones]

normally when you lose vacuum to the a/c system the air defaults to the defrost vents.

when it's not working check if you have vacuum at the a/c-heater selector switch

[Gidg]

Thank you Cjones. A friend told me that too. So you are saying that if I switch the knob from a/c to defrost, I should see and feel something different and if I don't then it's a vacuum problem? That makes sense.

[RickMN]

sounds like a cracked vacuum line. They use plastic lines, not rubber.