Fwd: HELP! '86 5ks blower stuff

[Sandy Duffy <sandyduffy@home.com>]

>From: "Ken Keith" <auditude@impulsedata.net>

>If someone could help me out, I would appreciate it.

>The new motor works when he applies voltage directly across it, and the 
>control head (that GM part) was supposedly tested by a mechanic and works.
>This a/c blower control unit has heat sinks, BTW.
>Basically, he wants to know what the function of this thing is, so he can 
>figure out why it's not working.  (The blower doesn't blow when he tests 
>it)
>
Ken:

Its in the Bentley but the blower control unit takes a signal from the control
head and regulates the speed of the blower motor relative to the interior 
temperature of the car.  During the summer, higher inside temp=higher 
blower motor speed and more (hopefully) cold air coming in from the 
condenser.  During the winter lower inside temp=higher blower motor speed 
and more (again hopefully) hot air being blown into the car.  The controller 
is right out of a GMC late 70s early 80s HVAC system. I bought my control 
unit from a Chevy dealer for $50.00...a lot less than the $200.00 Audi wanted 
for it.  Stamped on the control unit is the GMC part number!  BTW the heat 
sinks are necessary because the blower motor consumes a fair amount of 
power when its going full tilt.  If the unit is not receiving the signal
from the
control head it obviously won't operate but if the blower motor is good,
most of the 
time this is the cause of a blower motor not operating.

HTH

Sandy