atc250r

I've been having the problem of the vents defaulting to defrost and the controls not doing anything from time to time. I've checked over all the hoses under the hood and the 4WD hoses are long gone due to the posi-lock being installed. When I tried it today, the controls would put the air to defrost and floor without any problem but moving it to either of the dash vent settings won't work. I think I can hear a vacuum leak at the controls when I set them to blow out of the dash vents so I'm guessing that the HVAC controls are going bad. In any case, does anyone know of anywhere on line that I can get a diagram of the vacuum system on the back of the HVAC controls? I'd like to make 100% sure that the controls are at fault before I go and order a replacement. For those of you that have replaced the controls, what kind of money am I looking at to buy a replacement? Anyone have the part number?

Thanks.

John

74dart

Have you looked unther the battery on the drivers side at the cruse control vacumme hose. The battery acid is bad to eat through that hose.

atc250r

Yeah, I should have mentioned that I checked that.

John

mrclean

Before you go buying parts, check everything first. Look for that vacuum leak, it may be something as simple as a loose or broken vac line. Unbolt the control unit from the dash and slide it out a little. You'll be able to check the upper part of the vac harness there. The lower part you can check by looking under the dash. HTH

Scubasteve

Vacuum guage is pretty cheap, might just pick one up and put it on.

The hoses do go bad from the vacuum pump itself and end up closing off inside.


Jason

atc250r

I don't think its the lines from the vacuum pump since all the positions are working except the dash vent not to mention that the vacuum for the power brakes works fine too. I've got a vacuum gauge but I'm really looking for a diagram or a how-to on diagnosing the HVAC control panel before I go and buy one. Thanks for the replies so far guys, keep 'em coming.

John

Busboy

I'm pretty sure that ALL the trucks with AC have the same vacuum sw. Just get one from a wrecker, but make sure that it has AC. I know for fact that the heat only vac sw IS different internally. Vacuum lines are 1 green, recirc act. 2 red defrost/floor act. 3 black vac reservoir. 4 N/A. 5 brown defrost/floor act. 6 yellow panel/defrost act. 7 N/A.

atc250r

Thanks Busboy. That list of what hose does what is EXACTLY what I was looking for.

John