Do I need a 12-volt heater motor?

August 1, 2018 | By Staff


The heater in my 1949 Dodge is hot from circulating coolant but the fan motor has not worked since I’ve owned it. A previous owner converted the system to 12-volt negative ground. I’m about to troubleshoot it with a multimeter but have a couple of concerns. Will the motor run backward due to the conversion from positive ground? If I find the motor is shot, are there 12-volt replacement motors available?


It is quite possible that the previous owner just didn’t bother to hook up the heater motor because it would have burned it up when he turned on the fan. And yes, it would run backward if switched from positive to negative ground.

Ideally you should go to a 12-volt motor or you could install a reducer that would go from 12-volt to six-volt, and such reducers are available. You can purchase them from:

Vintage Auto Garage

11040 Bollinger Canyon Road

Suite E-186

San Ramon, CA 94582

As for a 12-volt replacement motor for your heater, I would contact Andy Bernbaum Auto Parts for parts as well as further advice. Virtually anything you need in the way of old Mopar parts can be found at:

Andy Bernbaum Auto Parts, Inc.

93 Border St.

West Newton, MA 02465