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I asked a auto electrician why the wiper motor would go extra fast, warp speed, and what would be done to slow it down. His thought was that there is a problem in the motor, providing risistance, and that in a shunt motor as the wiper, more risistance causes the motor to speed. Up. He gave me the name of a repair shop that can test the motor for that kind of problem. My question to anyone out there is, What has worked to slow down the motor and has anyone had any luck in putting a motor/switch from a 122 to the bracket of a 544?
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Forum;
I ran across this old thread, and am bumping it back up to the top because I have a possible/likely cause of the fast motor, and some explanations which hopefully will help some owner: Fast DC motor running is caused by an open Field Winding
To effect a high motor speed on a "Cumulative Compound DC Motor with Long Shunt", the Field is deenergized...this is counter-intuitive (and there is a starting torque loss price to pay), but if the Field winding of your motor were to have opened up (for any reason), this would be electrically the same as placing the switch of a two-speed setup in the Fast position. (See Reference links)
If you're lucky, disassembly and internal check will reveal only an open connection to the Field coil (which can be repaired, and which will bring slower speed operation back)...if you unlucky, the visible connections are fine, but the Field coil is internally open (this is unfixable for all but motor specialists who will have special fixturing and techniques with which to wind a new Field coil of the right wire gauge and physical dimensions)...
However, the speed could STILL be brought down to slower by wiring in a PWM controller for a DC motor (alternates between applying full power and OFF at a rapid rate which translates to a slower motor speed, but still with decent torque...opposed to simply putting a Dropping Resistor in series and applying a reduced but constant voltage, which gives poor motor performance and also results in excess motor heating, not to mention the significant wasted heat in the Dropping Resistor).
Reference Links: http://www.sw-em.com/Windshield%20Wiper%20Systems.htm
...look at: Different Motors and Different Circuits, same Control:
...and: http://www.sw-em.com/Windshield%20Wiper%20Systems.htm#Reference_Information_on_Compund_DC_Motors
Info on Dropping Resistors: http://www.sw-em.com/Vintage_Volvo_6V_to12V_conversion.htm
...look down to "Dropping Resistors"
Hope this helps someone.
Cheers
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This is the first time EVER that I've heard a complaint about a PV wiper going too fast; maybe it's a 6 volt motor?
Bracket?
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Well, it could be, but I have two sets of wiper transmissions that were said to be for 12v 544 models, and they both go nuts when juice is applied. I slowed them down by putting a couple of resistors (ballast types, from GI Joes Auto Supply) in the juice line, fixed to a metal bracket so the the heat has a place to disperse.
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The motor voltage is conveniently stamped on the drive end, so you have to take the motor completely loose to see it. The 6V and 12V versions look just the same otherwise. I don't know of any other way to check this other than disassembly.
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OK, I will take a look at the spare and see what it says. It is a dupe of the one that is in use.
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I REALLY don't think more resistance would cause the motor to speed up.
More resistance = less current, at constant voltage = less power.
As far as I know, other things being equal, less power does not mean more
speed.
But, are you sure the leads to the motor are connected correctly?
--
George Downs Bartlesville, Heart of the USA!
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The power and ground leads are correct. I switched the other two around/back again and so no difference. The souce said in shunt motors (as the wiper motor) it goes against logic, but if the motor has a defect and is meeting resistance, the motor will speed up. However, externally, on the hot line, I have a ballast resistor that does absorb some juice and does slow the motor to a reasonable pace. Heat builds up but never gets too hot to touch the metal bracket it is on.
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Well, I received my wiper delay kit in the mail yesterday, and I was puzzling about the wiring, as the diagram goes against all that I know about electronics and how electricity works. It looked like someone trained by the US Navy had drawn them up! Did you now that the Navy teaches the electricity travels from ground to positive?
The theory about shunt motors working the other way around may go a long way to explain this.
I don't have time right now to try to install the delay kit, as I have to make a trip to see the doctors about this broken pelvis...but I'll be home again in a few days and I'll see if the directions are correct.
In the meanwhile, it sounds to me as though you have a 6V motor. The 12V motor wipes only on one setting (I'd call it HIGH) but it shouldn't be at Warp Speed.
I had a 1946 Chevrolet sedan that had vacuum wipers, and after I repaired the little vacuum motors, it would throw the wiper blades a good 100 feet. now THAT'S Warp Speed!
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Did you now that the Navy teaches the electricity travels from ground to positive?
Ahem.
I was an enlisted electronics tech in the Navy '71-'75 (not counting a few years in the reserves), and I came back and worked for them as a civilian '89-'98. I taught an awful lot of sailors electronics as part of my job, and that's the first I've heard of current flowing towards greater potential.
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Guys;
That's the difference between "electron flow" (which flows from the positive treminal to the negative) and "hole flow" which flows in the opposite direction...both had eras when their teaching was favoured...it does make for problems when those who were taugh in different eras get together without clarifying...but when it comes down to it, what's the difference which one you learned...as long as you understand that when there is a voltage difference, current flows, and as long as you don't "change horses mid stream" as they say.
I happened to have learned that "holes" (or the absence of electrons) flow from the negative terminal of the battery to the positive terminal...whatever...
Cheers
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Ron, I remember that hole flow thing from the semiconductor phase of electronics school, but always found it so unintuitive that I banished it from my mind as soon as the final test was over... (If a train goes by, the holes between the cars are going in the opposite direction? No!)
Of course you're right -- it really makes no difference, as long as you think about it whichever way works for you.
8^)
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Phil;
The train analogy is not really a good one...how about the "bucket brigade" one...as the buckets are passed in one direction, the holes between seem to move in the other...
Maybe this belongs in another forum....
Cheers
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