VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt 6V Heater Motor and Switch

I've had my 54 3100 for a couple years but never bothered wiring in the heater motor when I put the new harness in because it doesn't get cold enough often enough to worry about. Still, for a few bucks and what I thought would be a simple install, I bought a switch and tested it out. The fan runs fine on High, but if I try to turn it down a bit, the rheostat gets HOT, as in smoking. I could live with it as is, using high on the rare occasion that I use it, but I worry that the switch could inadvertently get turned and create a fire hazard. I feel like I am just missing something simple, any advice would be appreciated.

Could it be a switch meant for a 12V heatr motor, which would draw half as much current?
Wilson

I agree that the first thing to check is the amperage rating on the switch. I also wonder if the motor needs cleaned and lubricated. It could be drawing more current at the lower speeds than the resistors can handle.

I think this may be one of those occasions when a new replacement control isn’t up to the job. They do get very hot because they are dissipating a lot of heat. There could be an oily substance on the control that is burning off.

Thanks for the suggestions. The new switch is from Cot40s, identified as a 6 volt, but I also have a vintage 6 volt switch that I tested on the motor with the same result, stressing again that it wasn't just very warm, it was fire hazard hot.

I have already opened up the motor to clean, polish and lubricate (getting the rotor back into the brushes was a treat) with the same thought. If I have to, I can use an on-off switch, but I haven't seen anything that looks like an original, I remember these old rheostats from way back and like the way it looks.

Rusty, you mentioned checking the amperage rating, can you offer some guidance on doing so-what about testing the current at the lower speeds, seems like even an electrical novice like me should be able to do it with some instruction?

I assume that you have wired this circuit so it is on the "load" side of the ammeter. So that should give you a general indication of the fan circuit load at the various speed settings.

I assume that your multi-meter can handle maybe 10 amps. That should be enough for this circuit. Check with your dash ammeter first to make sure you do not overload your multi-meter. You can also simply connect your multi-meter in series between the power feed to the switch and the switch itself. Then connect the meter in series between the switch and the fan motor. The difference at the various speed settings is the amperage being consumed by the resistors.

I agree that resistor type switches like these are pretty inefficient. The energy not going to the motor is simply dissipated as heat.

I would also take some resistance readings on the motor itself as well as through the switch in the various speed positions when it is disconnected from the fan.

I will get some readings from my '37 and post them for comparison.

I am not sure how to confirm it but do not assume that you really received a 6 volt switch. About half the parts I receive through the major supply houses are not what is really expected or wanted.

As an example we recently installed what was sent as 12 volt taillights on a '49 3100 that was converted to 12 volts. Things worked great when we initially wired them into the circuit. The next day nether the taillight nor the brake light would work. After an hour of troubleshooting the circuit we could not find anything wrong with the wiring. My voltmeter and test light indicated that we had good circuits. So we pulled the lens off the taillight housings. Both 6 volt bulbs had burned out!

Thanks Rusty, this will be a weekend job at the earliest so take your time but I appreciate the advice and information. I've had my own experience with new parts not working and should have known better than to simply assume it was as advertised.