On the floor

[68crum]

Just bought a 83 silverado, with at one time all options. My problem is that the heater only blows on the floor. I know tht is run on a vaccum system but I don't know where to start. Any ideas?

[piecesparts]

Take out the glove box and look on top of the heater core housing. there is a control arm there. That is the first place, then take the panel off under the steering column (four screws) and then remove the plastic air duct from the heater tothe air vent by the driver. Now look at the vacuum diaphragms that are on the end of the heater housing. That is your access to two of the control points, look to see if the cable is makeing the damper move behind the glove box and see if when you select a different position on the controller that the diaphragms are moving the dampers. I also believe that there is admaper that is up out of sight under the dsh that you can look at once the glove box is removed.

These trucks had problems with the control panel cable breaking or the vacuum switch not making good contact. That can be remedied by doing a replacement of the switch.