ktbr wrote:


It was a Lamar. I didn't write down the model number. It was for a 14V
aircraft, probably a Piper, meaning that the regulator sinks the field
current.

Piper electrical systems source the field current. The other side of
the field winding is connected to ground.

My Comanche regulator grounds the field wiring. I thought most pipers
were that way.

I should have clarified. The Cherokee line uses "B" type regulators.
For those, the regulator is connected between the power buss and the
alternator. Higher voltage at the regulator output (average voltage for
PWM regulators) yields higher alternator output. The other end of the
field winding is grounded. I wasn't aware the the Commanche used the
other type.