On Saturday I drove down to salt lake to look at a 1993 3/4 4X4 cummins. It happened to follow me all the way back to Montana.

The only thing that I have found that needs any attention is the heater box doors. The air is stuck on the head vents. It does not change to foot or defrost. There is a vacuum diaphragm on the left end of the heater box. the diaphragm is good. There is no vacuum no matter where you move the lever/which button you push.

There is a line going from the pump to the brake booster, a smaller line going back along the main line, and then a tiny line goes from the center of the the plug in the booster. The vacuum pump works.

What do I need to do?

 

Heater box has two cables I think if you pull the glove box out you may see them.

 

There is a multi colored clear headed plug behind the radio that distributes all the vac to the various gates. Make sure that didn't unplug.

 

I'm curious about this.. if you get it working can you throw some pictures up? Mine only does defrost..