Series Heater Wiring question

Hello. Series III Smith heater with resistor inside the housing, same motor as an MG. How do I connect the two terminals coming out of the motor - how can I tell which is ground and which is supply? Thanks, Riley

Attachment 14143
I recently rebuilt my heater from a 1969 88”. Hope these pictures help.

Hi there
Neither go to ground, they offer the resistance to give you the hi-lo speeds
If you have a multi meter, the one giving the highest resistance to ground will be your slow (?) speed.
Your dash switch should be wired to this accordingly.

Les.

Erik,

Thanks for sending the picture. An adventure indeed.

Best, Riley

Thanks Les,

There is only one feed from the resistor to the motor right? I have the original motor with two male spade terminals 180 degrees apart on the motor body. Trying to figure out which of those is ground.

Appreciate the reply.
Best, Riley

Riley
Yes, that is correct. What colour wires do you have? The original had green/brown and green/yellow wires. how they are connected depends on where they are on the heater switch, so a meter is needed for this also.

Hope this helps,

Les.

If memory serves, the brushes are not timed on the old heater motor so you could wire it ether way and one direction will pull air and the other will push. Check for resistance between the motor chassis and those wires to be sure. Shouldn’t be any resistance if I’m right.

If so, connect the wires to a 12v source one way and see what direction the motor goes. Wrong way? Swap the wires and it should go the other way.

For safety or if you are just worried about burning the motor then put a spade fuse in-line when you test. It will pop before the motor does. Try a 10 or 15 amp fuse. 30 amps would be a hard push if there was something wrong with the motor or debris or something else in the way of it working.