12V reduction to 6V wiper motor?

[Mountie B1]

I need to reduce the voltage going to my wiper motor. I tried a runtz reducer but the the voltage will not reduce (I tried a 2nd one in case the reducer was bad). Any suggestions on what I need to reduce the voltage?

Also, I reduced the voltage to the gas gauge. It worked for about a week but is now not working. Does anyone have any suggestions?

The truck is a 1948 Dodge B1C

[pflaming]

I'm trying to visualize the wiring under the dash. I think the wire to the fuel gauge comes off the ignition and maybe even the wiper motor. Whatever, if reducers are need for these couldn't one run one wire to the reducer and then from there to the fuel gauge and wiper motor. One wouldn't use either unless the engine was running.

I have ordered my alternator, coil, light bulbs, etc., to go 12 but didn't think about these two uses.

[chopt50wgn]

contact Newport Engineering. They are a aftermarket wiper company. Or call Ron Francis wiring. They have tons of parts for 12 to 6v cars.

[wallytoo]

i used "accessory voltage reducers" from classic parts of america for my heater motor and wiper motor. i used a "gas gauge voltage reducer" from the same place.

the acc numbers are: 24-996

the gas reducer number: 24-995

both the heater and wiper motor reducers have been installed for 3+ years, and work well. the gas gauge reducer was installed a few months ago, and is still working fine.

the acc reducers do get warm/hot when in use, so i mounted them under the steering column support.

[wallytoo]

I'm trying to visualize the wiring under the dash. I think the wire to the fuel gauge comes off the ignition and maybe even the wiper motor. Whatever, if reducers are need for these couldn't one run one wire to the reducer and then from there to the fuel gauge and wiper motor. One wouldn't use either unless the engine was running.

I have ordered my alternator, coil, light bulbs, etc., to go 12 but didn't think about these two uses.

i wouldn't run them to both. i'd also use a resistor designed to work with a gas gauge, like the runtz-style.

as i posted above, i've got three reducers installed. the gas gauge reducer gets installed directly to the gauge terminal, behind the gauge cluster, from its power supply.

[Mountie B1]

So you used 2 runtz for the wipers - one at the motor and one at the switch?  I tried this but the voltage is holding at 10.8?

[wallytoo]

not at all. no runtz for the wipers. a single reducer.

[Mountie B1]

OK and thanks - I just ordered the reducers from 'Classic Parts'.......  Thanks for the mounting suggestions.  Maybe this will solve the wiper issue.  BTW - I replaced the Runtz on the fuel gauge - seems to be working fine now.  Guess the first Runtz was bad.  This electrical part of the rebuild has been very challenging as I am TERRIBLE w/amps, ohms, etc!  GLAD TO HAVE THIS SITE FOR ADVISE/SUPPORT!  I have been off line for a while and still trying to figure out the new site........

[J.R.]

Sorry to dig up an old post but I am rewireing my 50 windsor with a new ez wire kit and have a few questions. I saw these reducers on another site and am going to order them but I am woderring exactly how many I need? I am going to keep the stock 6v electric wiper motor, stock fuel gauge and sending unit and I also have the M6 trans. I have a new 12v Speedway heater left over from another project so that is not an issue.

Will I only need 3 reducers, one for the wiper (wired into the power wire) one for the fuel gauge (wired into the power wire) and one for the transmission (wired into the power wire)?

I have rewired a lot of cars but never had any 6v left when I was done so I don't want to fry anything.

[wings515]

This may turn out to be technical but the way to determine if these "reducers" are correct is to do some voltage measurements.  The pictures show "standard" military grade high power resistors.  Something I used many many years ago.  To begin, use a 6 volt battery and an ammeter.  You can use the cheap one sold at Harbor Freight.  Connect the wiper motor lead to one lead of the voltmeter set to the AMP Current position.  Since it is digital, don't worry about polarity.  Connect the other lead of the voltmeter to the negative terminal of the battery.  Now connect the Positive terminal of the batery to a GOOD ground.  There should be no indication on the voltmeter.  Now turn ON the wiper, the current drawn by the wiper is now shown.

To determine the size of the resistor needed to run the wiper at 12 volts is to divide the current read into 6 volts.  Yes 6 volts because that is the difference between the new battery and the old wiper voltage.

Lets say the current was 1.5 amps.  The resistor value would be 6/1.5= 4.0 ohms.  Now to size it correctly for power dissipation take the voltage drop (6) times the current (1.5) to get a rating of 9 watts.  To be sure it is not under rated double the calculated value and round up.  So this would be 20 watts.

Now if you are going to use this for more than one device, they must be ON at the same time.  Wipers and gas gauges are not all the time, so you need to have independent resistors for each load that could be switched on and off.

Sorry for the long rambling.

On my 39 Plymouth PT81 I am using a 6 volt Positive ground Alternator with halogen headlight bulbs.  You can hear the alternator load down when I turn on the high beams but the battery is still charging even at idle!  I think changing the starter is more difficult than getting a 6 volt alternator.

Hope this helps.

Edited June 15, 2013 by wings515

[Plymouthy Adams]

was going to post a rule of thumb method to do this without the amp meter test but did not think it wise to confuse things...

Edited June 15, 2013 by Plymouthy Adams

[mike00]

also solid-state regulators exist. voltage can be dropped by diodes as well (zener diodes would work best) plus you dont have to worry about (probally minute anyway) changes in current, due to changes in resistance, due to things like temperature, load (how much water wipers are moving, and at what speed your traveling (wind pressure on the glass.) )