The Stovebolt Site Forums The Shop Area The Electrical Bay Original (6v) heater switch (AD)

Okay... I bought one of those flimsy POS switches for my '51 and I hate it. You can't clamp the thing on tight enough to keep it from sliding around unless you handle it with kid gloves.

Is it possible to use one of the original 6v switches on a 12v system with some simple modifications?

Let me see if I can keep this straight this time Woody. As Fred pointed out when we were discussing with the horn last week, when the resistance stays the same and the voltage doubles, the current also doubles, i.e. I=E/R. The resistor on the back of the switch gets really hot when dropping it's share of the voltage on a 6v system. Although the resistance of the motors is going to be different that dropping resister isn't going to change and being the other component of the series circuit I would say that it's gonna get REALLY super hot and would probably burn up on sort order.

Denny Graham
Sandwich, IL

I have one of the 6 V repro heater switches on my truck, which is still 6 V. The first new one I had melted when I tried to use it on anything but full power. I only use it on full power which means the resistor isn't used. I get the impression that the new switch resistors can't handle the current from the older 6V motors.

Have you replaced the heater motor with a 12 V? If so it might not be as bad. I must say that the amount of heat given off by my heater is quite minimal. The core is new and I use a 160 thermostat.

By the way, in case you haven't noticed, this is posted in the Radio Forum. I can move it if you like.

Argh...
Sorry... if you can move it I'd appreciate it.

Somehow we lost Denny's reply when I moved this post. Maybe he will catch that.

Anyways, I find that when I use my heater, I use it on full. It isn't all that affective so I don't need the resistor operation. If you cut the resistor then you will have it either off or on and that should work fine. Mine lights up when it is on and that is a nice feature.

Woody, I don't profess to be an expert at all but since the current draw is less with 12v and the 6v switch is designed to handle the extra current it should be a walk in the park for the 6v switch. Thinking back to when I converted my old 55.1 panel to 12v I kept the 6v heater switch and it worked fine.

When I temporarily changed my 6v truck to 12v and kept using the original 6v heater-motor switch and the original 6v recirculating heater, the back of the heater switch got hot as h%##. After switching back to 6v, no more hot switch.

I know very little about electricity, except how to follow color codes and how to use a multi-function voltmeter.

Okay so the resistor on the 6v switch is the weak point. Could I use the resistor from the 12v switch? Are resistors something that one can buy at Radio Shack?

If it makes any difference my heater fan motor is 12v.

Removing the resistor and having only one speed is definitely a viable situation for me so that's an option.

Woody - use an ohmmeter and check the resistances - might be different between the 2 switches, might not

Bill

Mt experience is that "probably" the resistor is the only difference. Resistors are also rated in power besides the resistance ratings. The power is the amount of power it can dissapate in the form of heat which is why they get hoy. Buy the highest power resistor that you can fit. That should keep you from getting one that will overheat and cause problems.

To over simplify and also working off of old education memories, the rule is that no form of energy just disappears. It has to be transformed into another form of power. A resistor takes electrical energy and transforms it to heat which it can dispose of through the air in the form of heat energy.

There are two cases here, one with the old six volt motor and one with a twelve volt replacement.

If you are using the old six volt motor than an external dropping resistor of about 1 ohm and a rating of at least 40 watts will work with the old motor and old switch.

If you are using a replacement twelve volt motor than a new twelve volt switch would probably work best. The variable resistor in the switch is sized with the charactersitics of the motor in mind and would be different from the six volt version.

Try this switch

Pete