# battery and windshield wiper problem



## palitorj (Dec 26, 2010)

I am using a 12v 2 amp supply and the windshield wiper motor jumps, instead of turn smoothly. It did turn for a second or so but I can't get it to go again. doing something stupid:?


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## niblique71 (Dec 2, 2009)

What kind of Wiper motor is it??? Our haunt group had problems with a few of those motors where the splines wouldn't grab well on the wiper motor arm causing it to slip or not grab at all. Perhaps you could describe the symptoms a little more thoroughly


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## palitorj (Dec 26, 2010)

*used motor that was used before*

We buy these motors used and have no idea what brand they are, no markings. This motor worked fine with a 12v lawnmower type battery and a supply of 12v 1.4A. A 2 amp supply couldn't cause the problem could it, the motor will just pull what it wants.
Could supply be bad?
I reversed cables once, but have always done this to change rotation direction.IU connect to the low speed terminal and the casing for ground.

Thanks


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## palitorj (Dec 26, 2010)

I didn't mention what the motor is actually doing. It rotates maybe quarter turn, stops, then rotates again quarter turn and does this continuosly.


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## bradbaum (Jul 26, 2008)

There was one people (including me) were buying from All Electronics a couple years ago, some of them seemed to have problems:

http://www.hauntforum.com/showthread.php?t=3785&highlight=wiper+motor+problems

This sounds just like the problems you are having.

I have had good luck just reversing the wiring, the motor seems to run in reverse just fine.


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## palitorj (Dec 26, 2010)

*power supply*

I just got the 1.2 amp supply. With this the motor runs fine. I don't get it. Motor is fine, its the power supply.
The 1.2 supply is for a modem or router, I don't remember which. The 2amp is a generic. The supply measures a steady 12v output on the meter, I can't measure amperage. How do you know what kind of supply will work.


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## Thisaintmayberry (Aug 23, 2010)

Could you be applying power to the "park mode" tang on the motor? Does the condition exist no matter which tang you apply power to?


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## Thisaintmayberry (Aug 23, 2010)

I'm also assuming that your power supply is DC. And you are correct the motor will only take what it needs so the 2A isn't the issue.


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## palitorj (Dec 26, 2010)

I use the same connection for the 1.2A and the 2A. Its the supply. I measured under load(duh) and 1.2 puts out a steady 12v. The 2A drops to nothing when motor starts. So that is the problem. Next question is how do you tell if a supply will have the guts before you buy it. I'm in Brasil so have much less selection than you guys. In general what kind of supplies are working for you?


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## niblique71 (Dec 2, 2009)

Many of us just use computer power supplies. Usually free from old computers that are being thrown out. Some are powerful enough to easily run 10 wiper motors. The added benifit is that they have 3V and 5V connections as well as the 12V to run other things you might have (LED lighting). The power is accurate, clean, and usually very reliable. Check with friends who have old computers, I'd bet you could score 10 of 'em in less than week. Most are very easy to hack into a usable power supply.


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## time2dive (Dec 29, 2007)

You might try putting a big capacitor across the power supply terminal. The capacitor will store some additional power and release it to the motor as it starts up.


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## Thisaintmayberry (Aug 23, 2010)

Concur with Niblique on the ATX power supplies. Cheap, plentiful and more than capable of supplying power. Wiper motors starting up under load can draw mega amps.


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## corey872 (Jan 10, 2010)

For this type of work, the old stuff is generally better. If you have a big, heavy 'wall wart' transformer, it is probably 'dumb' and just puts out what ever voltage/current it can. If you find one of the newer, light weight 'switch mode' supplies, it probably has a small circuit which times out for a few seconds if the current is over the limit.

You wiper motor probably has an inrush current of several amps on start up. This trips the protection circuit on the power supply, then it tries to start again, trips again, etc. This is what gives you the 1/4 turn at a time. As others have said, the capacitor might help, go scavenging for old wall warts or the computer supplies.


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## HomeyDaClown (Oct 3, 2009)

The difference is voltage regulation. If you use a supply that is not regulated, the output voltage will change as the load changes unless the supply far exceeds the maximum current being drawn. That is why your 2 amp supply voltage drops. I've run wiper motors on various regulated power supplies anywhere from 5 volt 1 amp to 14 volt 5 amp. You will also find that some regulated supplies do not have very good regulation as well and will exibit voltage drops under a load. There is one such supply sold by Allelectronics that is rated at 5 volts 3 amps that fails miserably after drawing only 1.5 amps.
Stick with supplies that are a little heavier duty than needed to get some breathing room.


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## Undertaker (Mar 22, 2006)

I ran into this same problem this past Halloween. I changed a prop from 12 volt battery power to a wall wart. Accidently I momentarily broke the ground connection to the wiper motor, when I reconnected the ground wire the motor ran just fine. I installed a on-off toggle switch in the ground wire. When I plug in the wall wart the motor starts in the "step mode" when I switch the toggle from on to off then back again it runs fine. Dont know how or why but why screw with success?


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## hpropman (Jul 27, 2008)

That is probably because the motor is already in motion and does not require as much current to start the movement again. when you start the motor from a dead stop the current draw must exceed the point set by the circuit and pulse. But when you switch the ground with the motor already moving the current draw must be under that threshold and runs smoothly. That is why some motors have capacitors on them to help them get started and then they run fine.


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