heater wiring

Dave53-7C wrote:

If your starter, lights and heater motor aren't 8 volts, I'd think their lifespan may be shortened.

That statement is true, if we still drove them everyday! They may only last 25 years instead of 50! All joking aside, The 6 volt headlight bulbs say right on them 6-8 volts. I have ran 6,8, and 12 volts. I personally don't like the 6 or the 8 volt. I had to turn up the voltage regulator to get the 8 volt battery to charge. I generally lost a headlight every other year or so, depending on the brand. Tung Sol is the worst lasting and the easiest to find when it comes to 6 volt bulbs. I switched to 12 volts last year and am very happy with it. I live in the D.C. metro area and prefer the brightest lights possible so the idiots on the road can see my tail lights and turn signals. It starts up nice and quick also. I can use/ hide modern 12 volt accessories now without having to have a battery in the trunk or one of those stupid 6-12 converters that have a hard time powering a decent radio unless you spend a mint on one. I can eliminate some of the spare parts that I used to carry because of the availability of bulbs and other 6 volt parts. 12 volts being HALF of the current than that of a 6 volt system means that my Rhode Island harness barely has to work to pass the current to my accessories. 6 volt positive ground systems were adopted from the British back then. They weren't a good system then, and still aren't. Suitable? YES. Efficient? NO. A lot of the vehicle manufacturers had already gotten away from or were working towards it while Hudson was shoving them down the assembly line. Some of the cars left the showroom floor with the grounding cable tightened up to the nicely painted engine block. Ask Wayne Wherle about that. He had problems with his convertible since he bought it in late 1954. IT ALL BOILS DOWN TO HOW MUCH OF A PURIST YOU ARE or HOW CHEAP you are. A lot of Hudson folks want to get by as cheaply as possible and use their 50+ year old harness and maintain a 6 volt system. When that no longer works, they step it up to 8 volts. It generally all ends up to an under dash fire and smoke rolling up from something. ANY system is good when properly maintained, but if anyone still has an old ratty original wire harness in your car that has electrical tape all over it, YOU DESERVE WHAT YOU GET.

Going back to the original post, the problem appears to be that the person installing the voltage-dropping resistor didn't appreciate the fact that it gets HOT! One has to mount such a device in a way that won't threaten nearby components. I mount the heater resistor inside the blower housing, fastened by a brass "strap" to the metal of the housing, so the heat will be transferred to that structure. By the way, the motor draws about 6 amps in the "high speed" mode. And to qualify a comment posted above, a device will draw about half the current in a 12v system IF that device is designed to operate on 12v. A 6v device connected to 12v will draw double what it draws on 6v.

By the way, in case anyone's puzzled by that photo, with the wire branching out into two wires before going into the resistor, it's actually two resistors wired in parallel. The optimum resistor is a 1 ohm, 50 watt rated one, but they're hard to find. I used two 2 ohm resistors of 25 watt rating. Wired in parallel, they provide 1 ohm resistance and a 50 watt power capacity (the resistors will be dissipating about 40 watts with the engine running and heater control in the "high" position ... dropping 7 volts, with 6 amps current. 7 x 6 = 42 watts).

Dennis, I'll accept the thanks indirectly, via your post above! LOL. Now if we could just find a good general purpose 6v relay, with contacts rated at 30A and having four terminal connections (i.e., the operating coil not "internally grounded"). NAPA used to make one, and considered reintroducing it a few years ago, but didn't do so. I've been unable, so far, to find a suitable one. Needed for use as overdrive relay and other purposes.

Dennis ... I'm an EE by education, but never worked in that field except at the supervisory level. I learned "the real stuff" from earlier days as an aircraft electrical systems instructor plus moonlighting doing electrical analysis and repair at a local garage. The later EE classes did explain some things at the "exotic level" that I'd not understood before.



The relay needed is one suitable for automotive use, an SPST with (ideally) screw or 1/4" blade terminals and a mounting tab, with cost under $20. The 12v "small black cube" types found at the auto stores, often in the "add-on driving lights and fog lights" section, are good examples. I've regularly Googled for such relays, but with no success yet. E-mail me at hetpwald@comporium.net (remove the "het" for actual address). Park

Nick, I have to disagree. Your explanation would apply pretty well to a series-wound motor such as a starter, but is not the case for a typical heater blower motor. You don't have the substantial "reverse EMF" to limit the current in this type motor. And it's really the current that makes a motor or any other electromechanical device operate. So, in your example, why would the motor run faster if the current were the same?

Surely you jest.