Jim G,

Did someone else convert the system to 12 volts? My guess is that the motor was also replaced with a 12 volt version...does it look 'newish'.

A old, stock motor would probably only have one wire coming from the motor...maybe two if one were a external ground. The three wires you have would hint at a newer, two speed motor.

A guess would be that the yellow is ground and that the orange wires would be a lo/hi speed arrangement. If you ground the yellow and momentarily touch each orange to power, does it appear to run at different speeds corresponding to each orange wire. Does it run the same direction using either orange wire.

The simplest switch arrangement if each orange results in a different speed would be some type of single pole-double throw toggle switch. This is all speculation...there are some weird fan motors around and they seem to wired in a non-universal manner. I wouldn't be surprised to find a dual voltage motor for that application.

Stuart