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EFV-8 Club Forum / General Ford Discussion / 1946 heater switch wiring with 12 volts neg ground

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Posted By Discussion Topic: 1946 heater switch wiring with 12 volts neg ground -- page: 1 2     headgearr 01-20-2010 @ 8:06 AM reply profile send p.m. Member Posts: 2 Joined: Jan 2010 I need to findout how to wire my original switch to run the blower motor? If not how do I wire the blower motor to run with an aftermarket switch. It has four wires and I don't what to do with this many wires. Also do I need to drop the voltage to 6 volts? 42wagon 01-20-2010 @ 8:25 AM reply profile send p.m. Senior Posts: 584 Joined: Oct 2009 Well to start with an original heater has a 6 volt motor and a 6 volt switch. I would think you will burn out the motor by running it on 12 volts. The motor should have 4 wires coming out of it. Three go to the switch and one goes to ground. The reason for that many wires is the motor is intended to run the fan forward and reverse. This allows you to either pull or push air through the heater coil giving you a choice of how the air is being blown around the car and also through the defroster nozzles. An original switch has a built in rheostat to control the fan speed and a light bulb to tell if the fan is on. curts41 01-20-2010 @ 9:30 AM reply profile send p.m. Member Posts: 32 Joined: Nov 2009 Thank you headgearr and 42 Wagon. I too am wiring a heater and also have 4 wires coming from the motor. Can you tell me how the motor reverses direction with the switch. I do not have a switch yet but do I need one with a speed control and ability to reverse. Any help would be appreciated. And please forgive the stupid question Curt supereal 01-20-2010 @ 10:27 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 The 4 wire heater motor and switch operates the fan in opposite directions by switching the polarity to the motor. One wire is ground, which you can trace to the body of the motor, one is a field center tap, and the other two are attached to the ends of the field. The control has two resistors that drop the voltage to provide a slow fan. I haven't been able to to locate my wiring diagram, but I'm sure someone has it. The original part number for the switch was 51A15122-B, which was superceded by 8C-18578-A. I don't believe it is reproduced. In any case, 6 volt motors can't be used in a 12 volt system. The high current draw is usually too high for the resistive droppers. Heaters were dealer installed accessories, in most cases, so the Ford number may not be appropriate. In most cases, the color codes on the wires are gone, so it takes trial and error to connect the switch. Just don't connect the ground wire to a "hot" source. 42wagon 01-20-2010 @ 11:21 AM reply profile send p.m. Senior Posts: 584 Joined: Oct 2009 Curt I suppose you could run the heater with a simple on/off switch by playing with the connection of the wires to it. But why would you want to? You would be loosing all the functionality of the speed and reverse control. The switches apparently are not reproduced but they do come up from time to time on E-bay and I'm sure at any big swap meet. Ted headgearr 01-20-2010 @ 11:57 AM reply profile send p.m. Member Posts: 2 Joined: Jan 2010 Do you mean that I cannot use this 6 volt motor with a voltage reducer? Some of these are rated up to 20 amp.If it can be run through one of these do i have to worry about positive ground vs neg. ground. curts41 01-20-2010 @ 1:34 PM reply profile send p.m. Member Posts: 32 Joined: Nov 2009 42wagon and all, I do not want to just hook up the heater without using all the controls which were intended for this application. I have determined which wires do what , and have started the fan. What I did not understand was why the blower seemed to intake air as opposed to blowing out. I did notice that the air went out in the right direction to the defroster but not into the car. Now, I think I understand how it is supposed to work. I have found several swithches on ebay, but no mention of a reverse. Will these switches work as far as the blower going in the right direction. I really don't care as much about the defroster as I do keeping the DW warm. Curt 42wagon 01-20-2010 @ 3:07 PM reply profile send p.m. Senior Posts: 584 Joined: Oct 2009 Curt Not sure what you are using for a switch. If its not the one intended for the job you probably have the wires connected in one direction. Switching the wires around will probably cause the fan to reverse and blow air out instead of in. The switch you need is cylindrical with a nut on the front side to screw into a small panel that bolts under the dash. Depending on which heater you have the panel may also have a remote cable for the defroster dampers. Some heaters have the defroster damper control on the face of the heater. Anyway back to the switch. There will be four connections on the back. One to connect to a power source and three to connect to the heater. You should find that the connections on the switch are color coordinated with the wires. The control knob on the switch turns in one direction for the air to blow out and in the other direction for the air to blow in. One bit of warning, heaters were accessories in the V8 era. Many cars never even had them. If you are expecting the creature comforts of a modern car expect to be disappointed. Oh they will deliver heat but just not what you are used to. Hope this helps Ted supereal 01-20-2010 @ 3:10 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 The "real" switch has 5 positions: Off, High, Low forward, and High, Low reverse. The heater is the three door variety. There is a good picture of the control and the heater on page 312 of the Club's excellent 1941-48 book. The knob next to the switch is to control defrost. Polarity is important. If you want the fan to work as per the switch, you have to reverse the wires for negative ground. I don't recall the current draw of the motor. When using a voltage dropper with a motor, you have to know the starting load, as well as the running load. Motors can draw lots of current. I've had several of these heaters, and I can say that you shouldn't expect lots of comfort from them. We are spoiled with today's "climate controls". The heaters are hard to find in good condition, as the cores usually are poor. oldford2 01-20-2010 @ 4:02 PM reply profile send p.m. Member Posts: 275 Joined: Oct 2009 You need the 4 terminal switch. low and high for heat, then pull the defrost knob and low and high for defrost. By pulling the defrost knob you close the forward duct and the reversed air goes up the defrost tubes to the windshield. I bought the correct switch from Stacy at Texas Antique Auto, Arlington,TX This 4 wire switch is not reproduced. John

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