question about the vac pump/defrost issue

***nismofan240*** · #1 (**permalink**) 03-03-2010, 01:21 PM

my hvac is stuck on defrost so i did the usual and ck all my vac lines. i found a broke vac line for my hub, where the bracket is for the 3 lines for my driver front wheel where they meet by the frame. so i fixed that, but my 4 wheel has always worked even with that broke line (well at leat the other hub was engaged) and 4 low worked. but my vac pum never comes on its dead quiet. so you would think that the pump is bad. but my question is if the pump never comes on why does the 4wd work. im gona test the pump later when i get a multimeter.

robthebuilder · #2 (**permalink**) 03-03-2010, 01:41 PM

You need to make sure the hubs disengage- maybe they are seized up, locked in all the time. Lift the front end of the truck and spin the wheel to check. You should be able to hear the pump when you are waiting to start.

Zaairman · #3 (**permalink**) 03-03-2010, 02:08 PM

You need a new vacuum pump and it sounds like your 4x4 hubs are already locked. Had the same issues with my truck.

CYates73 · #4 (**permalink**) 03-03-2010, 04:12 PM

the question is does it say it engages just when you do it auto? or do you have to get out and lock the hubs? but either way your vac pump is shot... it should be on... i can hear mine when im sittin in my truck to start it...

***nismofan240*** · #5 (**permalink**) 03-03-2010, 07:09 PM

yea the pump is shot, i threw my buddies pump on there and it worked great. my hubs are in auto, and the 4 wheel works great even with the crap pump. gona try to source a pump.

Zaairman · #6 (**permalink**) 03-03-2010, 07:53 PM

I think your hubs are shot too then. Reach behind the tire and grab the U joint at the knuckle... If you can't turn it, then your hubs are locked.

***nismofan240*** · #7 (**permalink**) 03-04-2010, 04:37 AM

hubs should be fine, it goes in and out of 4 wheel great.

Zaairman · #8 (**permalink**) 03-04-2010, 05:56 AM

Quote:

Originally Posted by nismofan240

hubs should be fine, it goes in and out of 4 wheel great.

I realize that... but with ZERO vacuum, your hubs will NOT autolock, which is why I'm saying you need to check your hubs to make sure they're not already locked.