Hot Rods Can we talk voltage reducer wiring, and windshield wiper park?

I'm confused about voltage reducers, wiring, and windshield wiper parking.

The 52 Plymouth I recently purchased has an original 6 volt positive ground wiper motor. The car has been converted to 12 volt negative ground.

As far as I understand the wiper motor is not concerned about the swap from positive ground to negative ground, so its no big deal.

The original switch (that doesn't seem to function) has 3 terminals (see picture) the post on the left side is the one stamped "P", an "R" is stamped between the two terminals on the right side. There were no wires attached to the switch.

The wiper motor has 3 wires hanging from it (all were cut), two wires came out of the transmission end of the motor, the other wire is attached to the wiper body near the armature on the motor.

For a test run, I attached a temporary ground wire from the wire near the armature to the dash frame of the car.
Then I connected a fused power wire to one of the two wires from the transmission end, and nothing happened. When I moved the power wire to the other wire on the transmission, the motor ran, and the wiper posts turned back and forth. I ***umed the first wire was for the park position on the motor, or maybe a motor reverse that is to park the wipers at the point when the switch is turned off?

Then I connected to a modern wiper switch I already had. The fused power wire connected to to the power input on the switch. The low speed wire on the switch connected to the wire that made the wiper run in the first test. With the switch in operation, I could turn on the wipers with the switch, and turn off the wipers with the switch. When the switch was turned off, the wiper posts stopped instantly, no park feature.
After the switch was connected and the wiper turned off and on with the switch, I tested the idea that the extra wires were for the park, or reverse of the motor when the power was first shut off. I connected a probe test light to a known good ground, and connected the probe to the second wire at the transmission area. I ***umed it would flash one time when the power was first turned off. While the wiper was running, the extra wire flashed the test light a lot like a turn signal works, ever few seconds, it would light up the light. When the switch was turned off, the wire was dead, never a flash. I'm confused. Any thoughts concerning the wiper park position?

In the process of connecting to the switch, I must have disconnected the ground wire I had attached to the motor, since the motor ran, I ***ume the wiper motor is grounded through the mounting brackets? I don't understand the reasoning for the added wire.

The voltage reducer wiring?
My plan is to install a 10 amp or 15 amp voltage reducer between the wiper motor and the switch. All of the heavy duty reducers I have seen have a pair of wires that connect to the higher voltage (in this case 12 volts), one for the 12 volt positive wire and one for the 12 volt negative wire.
Then there is a pair of wires that connect to the lower voltage (in this case 6 volts) , one wire connects to the 6 volt positive wire, and the other connects to the 6 volt negative wire. I understand both of the positive wire connections, the negative wire connections bother me a bit. All of the 12 volt negative wires connect to a ch***is ground, I ***ume I can just pigtail to a ch***is ground for the 12 volt negative wire connection? The 6 volt negative wire has me concerned. The wiper appears to ground through the mounting brackets, other then the loose wire that is attached to the motor housing, there is no 6 volt negative wire. Can I just attach the 6 volt negative wire from the reducer to a 12 volt ch***is ground as well, if not, where do I find a 6 volt negative wire for the voltage reducer?

 

Ground is ground. The 12 volt battery negative terminal is grounded. That is the same ground that the wiper motor uses.

If you ignore the wiper motor transmission, it would seem the motor wire provides power to the electric motor and the motor body seeks gound through its mounting hardware.

That doesn't sound like what you describe above, so that's not much help.

 

Here is a 10 Amp voltage reducer. It looks like 12 volts in one end and 6 volts out the other end, I ***ume in line with the positive wire.

https://www.speedwaymotors.com/Electric-12-Volt-to-6-Volt-Reducer-for-Motors,15824.html

 

First figure out which switch contact is which. With the switch 'off', you should have continuity between two contacts. If you don't have that, the 'park' or 'power' contact is bad. If that checks out, turn the switch to 'run'. Now you'll have continuity between one of the first pair (which will be power into the switch) and the 'run' contact. The now-dead contact is 'park'. No continuity, no running.

The motor has a ground tail on it because these were usually mounted on rubber bushings to reduce noise. The two other wires are your park and run power. The park wire should be hot at the motor when the switch is off. There is an internal contact in the transmission when the switch is turned off that opens that circuit when the wipers park. If the wipers don't park, that contact has failed.

 

NICE tech!

 

-6-Volt-Reducer-for-Motors,15824.html[/QUOTE]
That appears to be a 50 Watt, 1 Ohm resistor. It will not reduce much voltage on a low current draw load. The voltage drop (i.e reduction) is proportional to the current flow (Amps) through this device.

Russ

 

I'll add that not having that ground wire connected to a ch***is ground will cause the motor to seek another ground path, through the gears, linkage bearings, etc and will degrade those over time as well as likely causing motor overheating and/or intermittent operation. It's there for a reason.

As to the voltage drop resistor, I'm not a fan of these used on motors. As Russ pointed out above, the amount of drop produced depends on the load. This will also increase the total load, making the longevity of the switch suspect. Best practice is to determine the actual current draw under load of the motor, then sizing the resistor to that. I'm ***uming this was originally fused, find out what that fuse size was and figure actual running current at 80% of that which should get you close. Once you know that, you can then calculate the approximate 'resistance' of the motor and size the resistor. You'll likely need a larger circuit and fuse. I'd recommend running actual power to the motor through a relay to protect the switch. Using a standard Bosch-style relay, connect 12V power to the 30 terminal, the 'park' wire on the motor to the 87A terminal (NC), and the 'run' wire to the 87 terminal (NO). Connect the 85 and 86 terminals, one to ground and the other to the 'run' terminal on your switch. This will only work with a single-speed motor.

Best solution would be a 12V wiper motor, but that will require some fab work.

 

From past experience:

The two wires at the end of your motor are for park and run.

With the wipers off park should have power. Run should not

With the wipers on run should have power and park should not.

Thank god it’s not a later Chevy with switched earth as they just confuse the hell out of me!!

 

Is there a chance that Chrysler used that same wiper motor body, updated for 12 volts, in mid to late 1950's production cars?

 

It appears that Mopar changed their wiper motor designs almost yearly in the early '50s, with different units even between the cars and trucks. AI claims that Newport Engineering made a conversion for the early '50s Mopar cars but if they did it no longer shows in their listings. It may be worth calling them. The only thing that turned up was this... https://www.ebay.com/itm/277650262348?chn=ps&_trkparms=ispr=1&amdata=enc:1rXUp_TGoR7m6Hh_CPpZb3w21&norover=1&mkevt=1&mkrid=711-173151-913341-5&mkcid=2&mkscid=101&itemid=277650262348&targetid=2449372253943&device=c&mktype=pla&googleloc=9033433&poi=&campaignid=23925491501&mkgroupid=197394622957&rlsatarget=pla-2449372253943&abcId=9407524&merchantid=137625004&gad_source=1&gad_campaignid=23925491501&gbraid=0AAAAAD_QDh_VtMrmbNwwEUhRK6sO0BU6S&gclid=EAIaIQobChMIndGb8LyllQMV_QCtBh0MZgZeEAQYBSABEgJKl_D_BwE
A 'universal' kit using cable drive so some brain sweat will be involved, it's not a bolt-in.

 

Bear with me as I am walking through as much as I can while not out in the shop.

The switch only has two positions. While looking at the switch as it was mounted in the car, with the switch rotated into the counter clock wise direction, there is continuity between the outer two posts. Based on the directional rotation of the other original switches, I would ***ume this to be the off or park position.

With the switch in the clock wise rotation position, there is no continuity between any of the three posts. I am ***uming this would be the on position of the switch, if it was a good switch.

As I understand, that means this switch is a one speed switch and is probably no good.

I have had the wiper motor running through a 70s style wiper switch. It turns on, and turns off with that modern switch, using only the low speed position (it just doesn't park). I can put the wiper arms and blades on the wiper post and run them, but all I have here is a GB GDT-190A meter, and about all I understand about using it is DC voltage, and Ohm meter. I see it has a DC A area, but I have never used it, I don't even know how to place the leads. I suspect that could give me the running amps the motor requires? AI says a 52 Plymouth electric wiper usually requires a 10 Amp fuse.

I don't know how to post a link here from the bay place. The voltage reducer I was looking at was a 20 amp (the same outfit also has a 30 amp, a 15 amp, and a 10 amp, 12/24 volts to 6 volt voltage reducer). It would probably show up under a 30 amp 12 volt to 6 volt voltage reducer search.

I'm not apposed to the idea of a wiper relay, but that only protects the wiper switch, correct? I would still need to reduce the 12 volts down to 6 volts. I don't anticipate this car leaving home in the rain, the wipers are simply for if we get caught in rain and need to get home. I hate RainX!

Newport engineering says they have a 40s to mid 50s wiper conversion that uses the original wiper posts and blades. I'm not concerned about doing conversion work if I have to, I have moved entire modern wiper systems into older vehicles with split windshields before. That involved building wiper motor mounting points under the dash, transferring the modern wiper posts, creating linkage, and cutting down the wiper arms and blades.
The wiper system on this car is complete and would function with a switch and a 6 volt power supply. Reducing the 12 volts down to 6, or buying a bolt in wiper conversion has to be easier then moving a modern system into the car.

Years ago I had a 54 Dodge pickup with a 6 volt electric wiper I ran on 12 volts for 3-4 years. I would run it for a few strokes and then shut it off, sort of like an intermittent wiper worked. I did OK with that until I got into a real rain storm where I couldn't shut it off, it ran continuously for probably 5 minutes before the motor let the smoke out. I would rather not have that experience again.

 

Gene: I just did an easy electric wiper conversion. I found an old wooden bodied motor home that donated a wiper motor. The key here is that these vehicles have two separate wiper motors so the motor has the back and forth motion that the old vacuum motor has built integral onto it. Just need to adapt the pivot arm off the old vacuum motor onto it and you are done. All the old wiper transmission stuff gets retained.

 

Maybe mate a 12 v motor to the gear box? But 12v to 6 v converter might be the easiest solution.
Dan

 

This 6 volt wiper motor and what ever linkage it has, moved both the drums on the wiper posts on the cowl. I haven't crawled under the dash and inspected how Plymouth did this wiper linkage, all I know is that it does function at the posts on the cowl, and I have brand new wiper arms and blades that came with the car. The original wiper switch on the car is dead, there is only continuity between two terminals on the switch when its in what I would consider the off position, and no continuity in what I believe should be the on position between the 3 terminals on the switch.

I think, I may run the power through a relay like @Crazy Steve suggested so I can get a "park" power wire, then add a 15 Amp 12 volt to 6 volt voltage reducer on the "on" power wire going to the the motor. I'm hoping the 12 volts to the "park" power won't have much effect on the motor or the relay function. If it causes a problem, I will drop the "park" power wire, if I can't make the "park" function, I'm OK with that.

I do want to thank you guys for your help, especially @Crazy Steve.

 

The motors current draw varies with load as you say, it peaks at zero rpm = during start. Unfortunately this can lead to a situation where the correct resistance fir the normal running load drops so much voltage on startup so the voltage isn't enough to get the motor moving. If left on like that things may fry.

Resistors aren't great for controlling motors, the unbalanced nature of the motor doesn't play very well with a steady resistance.
There are so many ways to regulate a voltage using electronics these days (well, since the 70s at least), producing a steady result. I know it might not be traditional, but once in a while function may be allowed to have priority.

 

Well stated.

 

Let's see if I can clarify this more. Resistors are fairly commonly used to control motor speeds, with a prime example being 3 speed heater/AC fan motors. They work here because as speed drops, so does the load. It's when you have a variable load at a steady motor speed that they struggle. When multiple speeds are wanted under those conditions, the motor suppliers use multiple motor windings instead, generally limited to two speeds. Modern electronics now offer more options but those aren't really applicable here, both for cost and complication issues.

The first hurdle is what size resistor. The sellers aren't really giving you the information you need. Saying that it's a 12 to 6 volt drop @ whatever amps isn't everything you need to know. The critical measurement is its ohms value. Too low, and you drop too much voltage, too high not enough. You'll never get it perfect, but the closer you get the better it'll work.

The next hurdle is just what 'resistive' load the motor presents when running. Motors are NOT resistive loads, they're inductive, but you can approximate this value by knowing the running current under load. To find this, you'll need to mock up the wiper arms/blades and actually run the motor while measuring the current draw. Don't use your multimeter, as those are limited to 10 amps max and exceeding that will at best blow the internal fuse, maybe kill the meter. Current inrush when starting the motor will exceed 300% of running current. Instead, round up an ammeter in the 15-0-15 or 30-0-30 range and connect that in series with the motor lead @ 6 volts. Run the wipers, using both a 'wet' windshield as well as a lightly damp one (more drag) while looking at the ammeter to see what it draws. Look for a 'high average' in meter deflection and note that value. I suspect it will be in the 6 to 8 amp range, although if you see a higher number I'd start seriously wondering about whether the motor is approaching it's end of life. Also note actual voltage going the motor while running. Using the formula ohms = voltage/current will give you the 'resistive' value of the motor. You want to get as close to that value as you can with the dropping resistor, slightly more would probably be best to avoid undervoltage. Lastly, what 'size' resistor do you want? These will get HOT in operation and while they're giving you an amps rating, what you really want is a watts rating (which will be shown on it). Calculate this using this... watts = current X current x ohms. The resistor must be rated in watts at least that big, bigger is better as it will tend to run a bit cooler.

And if you use a relay, all you need is a simple on/off switch. By the way, I did see a NOS wiper motor on eBay if yours is iffy... That failed switch could have been killed by the motor.

 

On the paragraph about the resistor value, it seems that you might have the statement backwards. The higher the resistor value the lower the voltage at the motor, and vice versa.

 

If I were to make a voltage reducer I would make a PWM (Pulse width modulator) style reducer. Not only will it reduce the voltage, but can control the speed of the motor.
Also, there are many "switching regulator" IC's available that can do all of the above and more. They can be configured to measure current and shut down the circuit when the current exceeds a value. Since the PWM is just changing pulse width and the pulse always has 12 volts when High and 0 volts Low, power consumption is much lower than a resistor reducer, therefore less heat and more efficiency.

 

This wiper motor is described as single speed.
https://www.ebay.com/itm/326021006096

 

Photos here show a switch that looks different(?) from yours?
https://www.ebay.com/itm/326853820643

 

https://www.ebay.com/itm/3068056831...MI_JDLlayolQMVjiCtBh01PwDnEAQYASABEgICjvD_BwE

NOS stock motor.

 

@Crazy Steve , that Dodge motor looks different than the Plymouth motors in my links above.
Correct?

 

Wow, the amount of information that shows up here after a guy takes part of the day off!

If you could provide a link to a PWM that will reduce the voltage from 12 volts down to 6 volts, while providing 10 amps, that would be great.

I just looked into the PWM, its probably going to be way more of a learning curve then I want to get into at this time, for this project.

 

I'm surprised at how many wiper motors are available for this era Plymouth.

I have not really climbed under the dash and looked at this actual wiper motor, my original goal was to see if it even ran, which it does (on 12 volts). Then I just wanted to reduce the voltage so it wouldn't melt down, didn't sound too hard to me, but that introduction to electronics, single semester long cl***, I took in high school back in the early 70s was a long time ago (the instructor lost me when he told me I had to know what the color bars on a late 60 resistor meant, good thing my best friend was into electronics).

If a replacement wiper motor is going to be needed, I believe Chrysler changed from 6 volts to 12 volts in 54 or 55. I would be looking into making what ever modifications would be needed to install one of the earlier 12 volt wiper motors to this car. I suspect that if I stay with the early wiper systems that still had the bolt on wiper arms, the change over wouldn't be too hard.

My online searching skills are not very good, especially with out a specific model year or a car model.

 

It looks like the first year for 12 Mopars was 1956.

 

12 volt wiper motor photos here:
https://www.ebay.com/itm/298147816286

 

If I was to build it I would probably go for PWM, but if I was to buy something it would more likely be a buck regulator (good words for your search) as those can be found very cheap these days. Something like this in the link below. The difference is that the PWM turns (most of) the full input voltage on and off rapidly to provide something that works like a lower voltage out, i.e. 12V 50% of the time and 0V 50% of the time works much like 6V all the time for simple devices like light bulbs and electric motors - but not good for more sensitive electronics like radios.
A buck regulator converts the high voltage, low current coming in to a low voltage, high current going out, so it provides a solid, stable 6V out, and more current than what went into the converter. Efficiency can be over 90%, so little waste heat to manage (unlike the simple series resistor).

https://www.amazon.com/dp/B07Y7YB14L/?tag=atomicindus08-20

 

This might not work going from Negative ground 12 Volts to Positive ground 6 Volts. From the link above: "One important note: The product has no reverse voltage protection, so connecting power with reversed polarity can damage the board".

You should be able to make this work for Negative ground 12 Volts to Negative ground 6 Volts. I don't know if the original wiper motor cares about polarity - I took that cl*** over 60 years ago...

EDIT: Many direct current motors reverse direction when the electrical polarity is reversed.
Russ

 

The wiper motor runs in the correct direction with a 12 volt negative ground wiring.
I just need to reduce the voltage so the 6 volt motor does not melt down.