cruise control servo - GM type

[Will McGonegal]

For a while we used the stock GM electronic cruise control units to do throttle
control while testing engines on dynamometers at our lab.  The unit has a
stepper motor (3 phase) and another solenoid to engage/disengage the stepper
motor.  This is handy if you need to disengage the stepper and close the
throttle quickly.  We didn't use the built in brains (which normally accepts a
pulse speedometer input, resume, brake, coast, accel inputs), but tapped into
the stepper directly to control the throttle cable.  It worked OK, but was a bit
slower than we really wanted.  I don't think it costs much, around $200, but I'm
not sure, Someone else purchased the units.  The wiring diagram form a GM manual
specifies what the input are if you choose to use the GM on board brains.

Will McGonegal
Emissions Research and Measurement Division
Environment Canada