Dave,
I tried pretty hard to understand the complexities of the Autotemp
system but ran into a roadblock with the amplifier in the brain.
The servo unit is pretty simple -- the vacuum level applied to the servo
causes the diaphragm to move back and forth. The diaphragm is connected
to the big contact arm and that moves to determine blower speed. A
rotary vacuum switch determines air discharge location (floor or vents)
according to vacuum level, too. IIRC the one end of the contact strip
is for max blower heat, the opposite end is for max blower cooling, and
the closer you get to the middle of the strip the slower the blower
runs. There's a feedback potentiometer on the contact strip so the
amplifier knows where the wiper is.
The amplifier takes a resistance value that comes from a combination of
the ambient temp, in-car temp, and desired (dial setting) temps and then
controls the transducer.
The transducer then modulates the vacuum level to control the servo.
>From what I've seen the system was GM designed and originally appeared
in the early 60s on Cadillacs. I think it was called Comfortron on Olds
and Chevy cars. Anyway the components sure look the same. I had a 79
Seville and the servo unit looked nearly identical.
Here are some more pic links:
http://www.bos-engel.com/imperial/amplifier.jpghttp://www.bos-engel.com/imperial/servotop_s.jpghttp://www.bos-engel.com/imperial/transducer_s.jpg
I'll be away from my pc until the middle of next week so I hope these
tide you over.
Pete in PA
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