vents dont blow air

[t4llguy]

hey i got a early 99 powerstroke f350. now that its cold i just noticed a few things about the truck. i just bought it last may so this is the first winter i have had it. the problem is that the heat doesn't blow out the vents. i checked the vacuum pump and i noticed it wasnt working so i bought a new one. the new one works and turns on but it doesnt turn off. so i assume i have a vacuum leak. so my question is there any common place that the vacuum lines can break? or could something else be broken. i know the heat works because it kinda comes out the defroster vents and let it sit long enough and the truck gets warm inside.

[SuperCrutyPS]

Do you have 4wd? Do you have an ESOF (Electronic Shift On the Fly) switch on the dash?

The truck uses vacuum to lock in the hubs if their in the "Auto" setting. Many times the lines running down there break. Might wanna take a look.

[mikeandmary]

blower defaults to defrost in the event of vacumm leak. im no expert, but i've had the problem before. if you have automatic 4x4, it's operated by vacumm and thats likely the culprit. easy way to test... your front hubs have a vacumm line running to them. put your heat on the floor full blast, pull one of the vacumm lines and plug it with a golf tee. give it some time (maybe 30 seconds, cant remember) if that wheel is the culprit, the heat should switch to the floor, if not try the other one. if either or both cause the heat to function properly, you've found your leak. do a search here for front hub repair and youll find a wealth of info, and links to step by step repair. very common problem.

also check the lines themselves by plugging where they connect to the pump.

good luck

[t4llguy]

yes it does it has both. i will take a look at those in more detail i kinda looked at them when i changed the front springs

[t4llguy]

wow thanks i never thought of plugging the lines. i guess if thats the culprit i could make a quick repair to have heat until spring. thanks alot