GM-GMC: 81 gmc vandura heater blower, gmc vandura, air flow control

Question
hi there mr jacobson

i have recently purchased a 1981 gmc vandura g2500 and have a problem with the heater blower... it only works on high speed and i am unable to direct the air , it all comes out on the windscreen.is there a cable operating the air flow control or is it done with vacuum???

thank you in advance

al

Answer
This answer is in two parts:

A blower that only operates on high speed usually has the resistor bundle burned out.  This bundle is mounted so that it get air from the blower motor to keep it cool and has about four wires in a connector attached to it.  If it is not this resistor bundle, then it is the switch on the dash.

Second part:  If your vehicle has factory A/C, the air discharge control is accomplished by vacuum.  Either a vacuum hose has come loose (or a hole has been rubbed in a hose), or the selector switch in the dash is bad.  If you do not have factory A/C, the air discharge is controlled by a cable.