Wiper options after 12V negative ground conversion.

[Racer-X-]

Purist "all original restorers," I already know your opinions.  The car arrived with a 12 Volt battery in the spare tire well in the trunk, and a non-Mopar engine (LS1) under the hood.  It's a restomod.

 

Nothing has been done to the wipers. There's an antique looking wiper motor up under the dash, and a switch up there as well that looks fairly original.  I have no idea if any of it works.

 

Elvis (the car) will be driven in the rain.  So far, praying for sunshine and applying plenty of Rain-X to the windshield has worked. None of his events have had rain. But I'm living on borrowed time and that's not a long term strategy that's going to work. During the holiday break, there's plans to address this with a better solution.

 

I see 3 basic options:

 

• Carry two small "extra" 6V AGM batteries in the battery box (I have room there for two small "game camera" type 6V AGM batteries) wired in series.  Run the wipers off the one that's grounded at the negative terminal. This one has the advantage of being the simplest, but I'm carrying the weight of an extra 6V battery that isn't used, except to load the charging system to keep the other 6V battery charged. Also, I'm drawing alternator current to recharge one battery through the other battery, potentially overcharging the battery attached to the positive side and leading to short life for that battery. It just feels like something "Bubba" would do, and unprofessional.
• Obtain a 12V wiper motor that fits.  Not sure if one is available. Or possibly send the existing 6V motor to and electrics shop to have it rebuilt/rewound for 12V.
• Install a Constant Voltage "Buck Converter" module adjusted for 6.5-7.5 V output constant voltage.  These things are on Amazon, and one that can power 20A/300W is under $20. I'd need a box to put it in, but it's still a neat, clean solution I think.  I'm just not sure what current the 6V wiper motor draws both for operation and at start up.

[Sniper]

Might talk to these guys and see what might work

 

https://newportwipers.com/product/1949-50-dodgedesoto/#wiper-motor

 

I used a home made current regulator to control my 6v wipers on 12v.  When on full 12v it looked like the Tasmanian Devil whipping back and forth, with the regulator I built it's much slower, about what low would be if it was a two speed wiper setup.

 

So I guess I'd say go with the buck converter.  20A is probably enough, I dunno what the fuse is rated at for the wiper though that would be a good guide.

 

[Racer-X-]

I was thinking that 20A might be enough. But I'm not so sure.  All my modern cars use 20A or 25A fuses for the wiper motors, and that's for 12V motors.  6V motors tend to draw more current.

 

I need to lube and clean up the wiper transmission linkages and pivots first.  Then I might put a 6V light bulb (headlight bulb) in line with the motor and hook it up using the light bulb as a current limiter to see if the motor works and can operate from the lower current limit (that'll allow about 10A to flow).

 

Does anyone know the proper fuse size for the wiper motors in these cars when they had electric windshield wipers?

[Andydodge]

My car being an Oz assembled car used a 6volt wiper motor but when i installed the V8 etc I used a voltage resister for a few years but then changed it over to a 12 volt BMC/Lucas cable drive wiper motor installed between the glove box and passenger cowl..........works fine and the cable brackets can be adapted to either "clap your hands" or "wave your hands" simply by turning them upside down.........the Newport Engineering setup is very similar to the BMC ones............andyd  

[laynrubber]

I am currently using, sort of, a voltage dropper. Except it doesn’t work. I bought it from a large website that offers various vintage electrical components and they have no idea why it doesn’t work and no refund. Having said that I believe this is still a an economical answer to our dilemma. Finding a motor that fits or converts….I have searched and nothing under $200.

[Andydodge]

I used the same type of resistor that I used on the coil........it just dropped the voltage............got it from the local parts place.......andyd

[James_Douglas]

The 1946 to 1948 Desoto wiper unit is a motor and gear box in one unit. Nobody is making a 12 volt version that I have found.

Hunt down a good regulated step down transformer that is rated at 100% more than the draw on the motor. It will last forever if you do.

 

James

[Sniper]

Step down transformers are for AC, not DC.  You need a buck converter.

[James_Douglas]

2 hours ago, Sniper said:

Step down transformers are for AC, not DC.  You need a buck converter.

Sorry I misspoke, but on purpose as most people have no idea what a buck converter is. They understand the idea of stepping down one voltage to another....hence my use of the term. Sometimes a descriptive term is worth more than the technical correct term to convey an idea.

 

I have extensive experience with such things. I had to design and spec a set of transformers to convert the 220V Delta Power (110V-110v) on our fleet of ships to 120V (0V-120V) power for all the computers, GPS and the like. Also, the 110V APC power supplies do NOT have fuses on both mains so in a ship delta power environment we had them catching on fire if there was an equipment issue. Which on the bridge of a $100M freighter with $800M in cargo was not a good thing.

 

James

[Sniper]

Problem with using a descriptive term for the layman is that they go looking for that item.  Which in this case would be an issue.

 

Simply put, a buck converter is a DC to DC converter that takes a higher input DC and puts out a lower DC voltage, such as taking your 12v and putting out 6v.

 

A boost converter would do the opposite, turn 6 into 12v for example.

 

These types of converters will more efficiently convert the DC, up or down, than something like a resistor or my current regulator.  Both of which turn the excess voltage into heat when turning 12v into 6v.  For the record a Runtz Resistor, which is used on a gauge when converting to 12, is more a buck converter than a real resistor. 

[Racer-X-]

18 hours ago, James_Douglas said:

The 1946 to 1948 Desoto wiper unit is a motor and gear box in one unit. Nobody is making a 12 volt version that I have found.

Hunt down a good regulated step down transformer that is rated at 100% more than the draw on the motor. It will last forever if you do.

 

James

 

Actually, the buck converter is piling up votes here, and I don't think you've voted in the poll yet, just with a reply.

 

Does anyone know the rated draw for the 6v wiper motor assembly?   I was looking at 20A buck converters.  I suspect that will be enough, but I'm not entirely sure.

 

I'm also going to be checking parts yards while I'm out scavenging other parts for other projects, to see if there are any wiper systems that have the same center-center distance for the wiper pivot shafts.  A transplant from something else (with a 12 volt motor) might also be a possibility.  I'm not sure if we have the original wiper arms on Elvis.  They look really spindly, weak and very shiny.  Just like something a shop that's great at upholstery and paint would install.  Just sayin'.

[Andydodge]

All i know is that the voltage resistor that I used which was the same as that used when a "resistor" coil is used worked fine, even through the standard 1940 Oz Dodge wiper switch.....the reason the whole shebang got replaced was that the wiper tower washers that held the wipers on were buggered and back then, around 1980 unobtainable here in Oz so it was simpilier to just replace the whole lot, wiper, arms, etc with something that I knew worked and I could at least back then get parts for..............the wiper arms I used were short stainless arms that I had to heat & bent slightly and worked fine till 2-3 years ago when  I bit the bullet and bought nice new shiney stainless arms from Newport Engineering in the USA, these new arms are adjustable both in length and angle but by the time they arrived here in Oz a little expensive but as the BMC wiper towers use the standard 1/2" spline the Newport arms fitted fine.........

.............and if you are wondering how the centre windscreen bar remained so nice.....stop wondering thats a hand made one that I made from 1"x1/2" brass bar cut with a hacksaw lengthways and file finished then soldered to a tapered, drilled & tapped piece of 3/8th square brass bar then chromed.......done when I was young & silly.............about 45 yrs ago...........andyd   

Edited December 17, 2021 by Andydodge
more info

[pontiacguy]

Talk to Newport wipers. They are doing the motor for my 54 right now. They don't actually build one but they looked at some pics and said hold my beer. Newport stuff has the advantage of being 2 speed as well. They offer the correct switch to take my wiper knob, it will probably be correct for yours too. For the record, I am incredibly fussy. My car will be a nothing newer than 63 style build. I had to swallow hard to use their stuff because it doesn't fit into the spirit of my build but it's the best option hands down. They aren't cheap, but if money was the overriding factor, Id be in a Kia. That's my 2 cents. 

[chrysler1941]

The answer has been answered in earlier threads, Forget converters and resistor. Use a PWM module. <$10 on ebay.

[wallytoo]

i went the voltage reducer route in my truck.  installed the resistor to the underside of the steering column support, and have been using it for 10 years.  also installed a resistor for the heater motor.

 

 

 

[martybose]

I'll be the naysayer on this one.  Even though my car was converted to 12V eons ago, I stayed with the vacuum wiper.  Had the vacuum motor rebuilt, and installed a good size vacuum reservoir with a check valve.  Rarely drove it in the rain, but the few times I did the wipers worked just fine.

 

Marty

[ebruns1]

On 12/18/2021 at 4:59 AM, chrysler1941 said:

The answer has been answered in earlier threads, Forget converters and resistor. Use a PWM module. <$10 on ebay.

This seems like a great idea!  Are there any downsides?  I'm going to order one asap.  Assuming I need one that says 6V, 12V, 24V. correct so I can set it back to 6V to run the original motor.  Would a variable voltage be able to control the wiper speed?  It looks like the original wiper switch is already set up for 2 speeds (mine crumbled when I took it out so I can't tell what it looked like.)

[Sniper]

PWM doesn't change the voltage. 

 

https://www.kompulsa.com/introduction-pwm-pulse-width-modulation-works/

[SteveR]

On 12/18/2021 at 10:20 PM, wallytoo said:

i went the voltage reducer route in my truck.  installed the resistor to the underside of the steering column support, and have been using it for 10 years.  also installed a resistor for the heater motor.

These also generate heat and need to be placed in an open area as you did. Also being mounted on a large piece of metal will help dissipate the heat. The last thing you want is to set wiring on fire.

[wallytoo]

2 hours ago, SteveR said:

These also generate heat and need to be placed in an open area as you did. Also being mounted on a large piece of metal will help dissipate the heat. The last thing you want is to set wiring on fire.

 

yes.  that's why i mounted them where i did.  on a large piece of metal.

[SteveR]

9 hours ago, wallytoo said:

yes.  that's why i mounted them where i did.  on a large piece of metal.

I am running 12 volts in my 37 Plymouth but the heater fan motor was 6vdc. I could not get a 12 vdc motor in the UK to replace it and I was thinking of using these resisters. The problem I had, there was no place to safely mount them under the dash. I ended up using a step down transformer.

On 12/18/2021 at 10:20 PM, wallytoo said:

i went the voltage reducer route in my truck.  installed the resistor to the underside of the steering column support, and have been using it for 10 years.  also installed a resistor for the heater motor.

These also generate heat and need to be placed in an open area as you did. Also being mounted on a large piece of metal will help dissipate the heat. The last thing you want is to set wiring on fire.

[chrysler1941]

On 1/25/2022 at 10:54 AM, ebruns1 said:

This seems like a great idea!  Are there any downsides?  I'm going to order one asap.  Assuming I need one that says 6V, 12V, 24V. correct so I can set it back to 6V to run the original motor.  Would a variable voltage be able to control the wiper speed?  It looks like the original wiper switch is already set up for 2 speeds (mine crumbled when I took it out so I can't tell what it looked like.)

Typically they can handle 6-30v 

You have to measure your fan motor current and choose a PWM module with sufficient Amps.

Amps can be calculated using Ohms law, measuring motor windings resistance and multiply with voltage, typically 7.2v

 

Downside you may need to change the generic pot. meter for more variable speed. 

[Dartgame]

I used a converter that was outlined how to assemble on a VW bug site. Pretty easy. cost a few bucks to assemble it.