AC/Heat Won't Turn On

[DieselLT]

So my AC and heat will not turn on. It was working fine, then would only blow from the defrost, and now it won't blow at all. I understand the switch for the air is controlled by vacuum. Does anybody know what part I need to replace to fix this?

[matter]

could also be the blower motor

[DieselLT]

Still can't get my vents to open. Every once in a while they will open after hitting a bump and the road and stay open till I turn the truck off. When I turn it back on they will be closed again. Anybody have any ideas.

[daveyburt]

could be a blower motor AND a vacuum issue....can you hear the fan spinning when you turn up the fan speed?

[matter]

there is a heater control thingy, can't remeber the name, but chase your heater hoses until just before they enter the cab, there is a section where they meet together, with a vacuum hose attached, but that would just not allow heat, since you say both heat and a/c, i'm also leaning towards blower motor, just to be clear, you have no air blowing in the cab no matter what setting you have it on, right?

[tipsyjack]

check the right side(pass.) under the hood by the cowl/evap box area,if i remember right there is a vacuum canister in that area,there is a vacuum line that goes to it that will go bad due to sun light hitting it.the light gets to it between the fender and hood gap.maybe the culprit,easy fix if it is.

[NCHornet]

You have a vacuum leak. The most common place is the back of the front hubs on a 4x4 where the line attach to a nipple, the hose splits and looses vacuum, cut off the damaged area and reinsert over the nipple. Another place is in the pass footwell there is a line that can get kicked loose. Of coarse it could be a bad pump as well, right now it should be running at all times because of the leak.

[Rohan]

My blower motor went out a couple months back. I could start the truck, get out, and bang on the motor with my fist to start it up again and it would be good for a while. I picked up a new one from a local parts store. They're not too expensive if you get a reman. Turn the ignition to 'ON' (don't start the truck) and cycle the fan speed from low to high. You should be able to hear the motor speed up whether the vents are open or not. The motor is on the passenger side up by the firewall under the hood, right up against the fender. It's easy to pull and replace if that's the problem.

If the motor is spinning fine, it's definitely somewhere in the vacuum system.