Newbie here. Recently bought a 2000 Excursion and it has some issues. The air conditioner blows out the defroster. The heater blows out the defroster, in fact that's the only place the blower forces air through. I read on another forum that it could be the vacuum pump. Of course that forum did not have any pics or explained how to troubleshoot, repair, or replace. It could be a vacuum leak, but the Haynes repair manual I purchased doesn't go to that level of detail. Anyhow, I need some advice/information. Where is the vacuum pump? What reading should be on my vacuum gage? Is there a common location where the Excursions leak? How hard is it to remove the dash?
For your info, my Ex does not have 4 wheel drive, but it does have rear air conditioner. Any help would be greatly appreciated.

 

We have a similar problem with our excursion. We found the vacuum under the hood on the passenger side just above the wheel well. If you turn the key to the run position but not start the car, when you open the hood you will hear the vacuum running. Our vacuum is running, but is not building up pressure. We are working on trouble shooting it now. Let me know if you find anything else out, and we will too.

 

That's the correct route to be taking. Also look for a vacuum leak in the vacuum lines under the dash. Sometimes somebodies toes get up under the dash on the passenger side and pulls a line loose. Default setting due to a vacuum leak is the DEFROST setting.