My daughters wedding is in Feb she wants to use my 48 panel in her wedding. I have converted to 12 volts but have never had a use for a heater so of course didn't worry about it. What do I need to reduce the voltage to the fan motor. It gets cold here in Nebraska.
I'd suggest using a speed control resistor from a later model vehicle in series with the 6 volt fan motor, one that has several connectors and is mounted in the ductwork with the blower air flowing over it to keep it cool. The wire-wound resistor in that setup can be tapped into at 3 or 4 different locations until you get the blower speed you want. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
If you use the voltage reducer that Tim shows above , just remember they get extremely hot and need to be mounted in a safe place. I would go with the 12 v blower motor like mark suggested.
Tim
1951 3100 Chevrolet 1951 Chevrolet Suburban Carryall Image "A house is built with boards and beams. A home is built with love and dreams." "Look deep before you leap !!!" / "Everything is Everything" "If I say a mouse can pull a house, hitch him up"
Assuming from your post you already have a heater unit and probably only an on/off switch just put a resistor like Tim suggested ( you can find them at better FLAPS or electric motor shops) in the line between the switch and the fan motor. Be sure to mount it clear of everything even including feet and legs. I actually took the wires through the firewall and mounted it on one of the heater mounting studs in the engine bay. Works like a charm.
Mount the resistor in the air stream from the fan. A piece of Bakelite or other phenolic plastic works as an insulator/mounting fixture, and a small rectangular slot cut into the ductwork puts the resistor out of reach and into the moving air stream. The heat it generates adds a degree or two to the output of the heater, also. It's the way OEM blower speed control resistors have been mounted for at least 40 years. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
You should have it wired in this order: Ignition 12 volt ON Switch > 12v to 6v Voltage Reducer > Fan speed switch > blower/fan motor.
This specific topic has been discussed before. It does not matter which order these components are arranged. In fact, you could put the resister between the ground wire of the motor and chassis ground and it will still work. Electricity is "special" like that.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
It does seem like vendors would sell a higher wattage resister. Tha'd keep the heat down.
What kind of resistor does not produce heat?
"Unlike lamps, they do not produce light, but they do produce heat as electric power is dissipated by them in a working circuit. Typically, though, the purpose of a resistor is not to produce usable heat, but simply to provide a precise quantity of electrical resistance."
"Wattage means how much power the physical resistor is rated to handle. The rating is always for given conditions, such as the ambient temperature, or when mounted on a heat sink. You determine the power in a resistor by computing the voltage across times the current thru it."
The electronic voltage reducers used with fuel gauges might be different, but they are not a resistor, they are an electronic device normally suitable in a low power-draw application.
Watts = Volts X Amps. If a 1 ohm resistor is flowing 5 amps of current it's dropping 5 volts across the resistor, and producing 25 Watts of power (heat). The same resistor would drop 20 volts and create 400 Watts with a 20 amp flow. The trick is to figure the maximum current an accessory will draw and size the resistor wattage accordingly. Using a too-small wattage rating will result in resistor overheating and burnout. Higher wattage capacity on a voltage-dropping resistor is always better, as they produce a LOT of heat as they consume voltage. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
"It does seem like vendors would sell a higher wattage resister. Tha'd keep the heat down." So, what size resistor would you recommend for a 12v to 6v heater-fan motor?
Let's say you use the Classic Parts resistor (shown below) for 12v to 6v heater motor, and you find it gets quite hot. What size/type resistor ("higher wattage resister [resistor]") would you use to decrease that heat under the dash?
Tim, What we need to do is to figure out the Wattage of the resistor being sold. I can't find mine. Presume that a call to Classic Parts might get us in the right direction. Then find a resistor with 2X,3X, 4X the Wattage.
The Classic Parts resistor is a one Ohm 50 Watt resistor. It's labeled, if you just zoom the photo a little. That's way too small. The 1 Ohm is fine- - - -(maybe)- - - -but the resistor needs to be rated for about 200 Watts or so to keep it from overheating. To figure how much voltage the resistor drops, it's necessary to MEASURE (not guess about) the current flow of the end item such as a blower motor, etc., with it operating with the resistor installed. The idea is to dissipate HALF the applied voltage with the resistor, and the other half with the motor, etc.
Example:
Engine running, battery terminal voltage is 14.5 Volts. The resistor needs to drop 7.25 Volts, and the accessory needs to run on the other half.
If the item draws 10 amps at 7.5 volts- - - -it's using 75 watts of power. The resistor will also be producing 75 watts of heat. There is NO substitute for measuring current draw AFTER the dropping resistor is installed, and tinkering with the resistance value until the accessory sees the voltage it needs.
THERE ARE NO SHORTCUTS! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
HotRod Using your math. The resistor is using 75 watts and pushing it thru a 50 watt resistor. We don't need the math here. We already know the resistance (thanks Jerry) All were really doing is to swap a 50 watt 1 ohm resister. With something that has a larger Wattage.
Here on Amazon is a 200 Watt 1 ohm resistor. Notice that it's rather large 1 1/2 times the width your hand. No problem were using it in a Truck.
four 4 ohm 50 watt resistors wired in parallel provide the 1 ohm required - - - -AND the 200 Watt capacity. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Mount the resistors on a piece of 1/8" thick aluminum, and you've got a good heat sink. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I called mouser.com and they will bend over backwards to get you the correct resistor for your application. Smart Dudes And they do sell to the public.
