[upsman64]

hope you pro's can help me , i got in my truck this mourning and no matter where i set the knob the air comes out the defrost,even the a/c blows out the defrost vents. any ideas?

 

[gregrob]

[ QUOTE ]
hope you pro's can help me , i got in my truck this mourning and no matter where i set the knob the air comes out the defrost,even the a/c blows out the defrost vents. any ideas?

[/ QUOTE ]

I'd say you have a leak in one of the vacume lines going to the hubs. You DO have a vacume leak somewhere, it is set to default to the windshield so it can still defrost.

If it's the ESOF lines, I would upgrade to the braided steel ones.

 

[upsman64]

where are the lines you are talking about, how do i check them

 

[gregrob]

[ QUOTE ]
where are the lines you are talking about, how do i check them

[/ QUOTE ]

They run down to the hub on each front wheel, I would inspect the for cracks, see if they're unplugged etc.

 

[mfife]

Go with what is easy first. Look at fuse 28 I think. It is the lowest 10 amp fuse on the fartherst right column on the fuse panel under the stearing wheel. Use a penny or a flat head screw driver to remove the cover below the steering wheel then remove the blak fuse panel cover.

 

[GreenMonster]

I had that happen twice on my '99, and it was the vacuum pump both times. Since these trucks don't gernerate vacuum like a gasser, and they didn't want to come up with a whole new a/c system for the diesel, they added a dedicated ( expensive! ) vacuum pump that only runs the a/c vent switching and maybe one other thing. Supposedly an easy swap, I had the dealer do it both times; it took so little time the second time they didn't charge me labor, just parts
Good luck,
Bruce

 

[Matt-M]

Since you are not 4X4, you do not have the "normal" vacuum leak at the hubs. The vents are activated by vacuum as has already been said and the pump is located near the fender well on the passenger side.
When you turn the key on, you should be able to hear it run for a short time and then cut off.
If if does not come on, then the fuse or the pump could be bad.
If it comes on but does not cut off, then there is a leak.

Matt