bigthumper

a friends a/c wont blow it just blows air out the defrost vents....

is that one way if so.... what would some other things be....

phox_mulder

That is most likely just a disconnected vaccum line.

Check the firewall, and along the cowl.
There should be a vac line there that tees off then goes through the firewall.

4x4 (prior to 2002.5) and cruise control both need vaccum to operate, if the pump was indeed bad, he would have at least those symptoms.
Some years (not sure which) also used vaccum for the power brakes.


phox

tool

Like Phox said.............

If the vac pump wasn't working, his power brakes wouldn't be working either, and they don't stop too good without 'em

torquefan

I have worked on these trucks for years and have yet to see a vacuum pump fail. They will leak oil, but you can reseal them. Your friend either has a vacuum leak, as Phox mentioned, or maybe a failed actuator on the mode door of the HVAC system.

Supermod56

Yep, they will leak like a sieve, but usually always pump. And all the newer trucks have a "Hydroboost" for the brakes, runs off the P/S pump pressure. Vaccum runs the dash controls and the cruise, also the exhaust brake if so equipped.