HVAC issues

[dpuckett]

In my 90, I am having trouble figuring out where to look next. I get decent blower speed, but air only comes out the dash vents. I have vacuum going to the controller, but nothing moving any vent doors. Once in a blue moon it will blow somewhat out the defrost. The defrost has to work to pass inspection, and that is really all I care about at this time. That, and getting some miles on it so I can check MPGs, ride, power, etc. Is the control unit fixable? Or am I stuck getting a new one?



Daniel

 

[Stanbery]

I'm eager to see what someone comes up with as I'm having the same problem with my '92.

 

[bgilbert]

All the vacuum hoses hooked up on the heater box? Drop the glovebox down out of the way to get a better look. Also manually grab the door linkages to see if they are froze up.

 

[dpuckett]

I know all the vacuum lines are hooked up, since I had to rob them out of the 90 to put in the 92. Then later, I got some more lines from a junkyard truck and instaled them in the 90. I'll check the doors tomorrow. Supposed to be remodelling the bathroom... ... ...



DP

 

[jdurham]

There are two problems I have found on these trucks. First, get a vacuum pump and check the actuators on the heater/ac box. You should be able to pull them down with the pump and they should stay. If they don't move, or they don't stay, replace them. Next, the connector on the hvac switch where all the vacuum lines run deteriorates and comes apart. At that point, you have a leak and your switch is no longer functioning. I have no idea if these parts can be purchased new, since I fished used ones out of donors.



Hope that helps.



Jim

 

[dodgenstein]

Defrost is controlled by two pots. The left side one if you look in the glove box opening chooses heat/defrost or A/C. The rod in this needs to be retracted for heat/defrost. The other pot is down by the accelerator pedal. When vacuum is applied, it chooses defrost. The first pot goes to a/c position when shut off. If you want a quick fix to pass inspection, pull off and plug the vacuum line toward the driver side and manually retract the rod. Then you can have defrost until you have time to troubleshoot w/vacuum gauge. Probably a bad connection somewhere, or crossed tubing after a heater or a/c service.

 

[dpuckett]

I found it- I had hooked up 2 of the vacuum lines backwards. Switched them around, and all was well. Well, except the blower could move a little faster, but I have it all back together and it is going to stay that way.



DP

 

[CGauthier]

You mean the blower doesn't blow very hard Daniel? If so I've been wondering about that, other vehicles I've had when you turned the fan on high you could really hear the air movement... this truck doesn't seem to blow very hard or get really hot either... .



Carl