Windscreen wiper motor questions

**bitem2k** · 17th May 2007 11:03 AM

I recently salvaged an old windscreen wiper motor from a car.

The Motor has four terminals. Ive got two of them connected and it seems to work fine, is this right?

I intend to run the motor for hours at a time, and i would imagine that they are capable of that. I sometimes drive for hours in the rain and i would have my wipers on for the entire time.

If i run it for hours, it gets realy hot, and stays that way for about 30minutes after i turn it off. Is it meant to get that hot?

Thanks very much.

**RODALCO** · 17th May 2007 11:29 AM

bitem2k

It shouldn't be too hot to touch.
Certainly you shouldn't burn your fingers on it.

What are you driving with it. The loading may be too heavy for the motor.

It is usually a series motor, check that the armature is in series with the field windings.

**bitem2k** · 17th May 2007 11:33 AM

Originally Posted by RODALCO

It shouldn't be too hot to touch.
Certainly you shouldn't burn your fingers on it.

Its def. hot enough to burn yourself on.

Originally Posted by RODALCO

What are you driving with it. The loading may be too heavy for the motor.

It overheats with no load

Originally Posted by RODALCO

It is usually a series motor, check that the armature is in series with the field windings.

Im sorry can you please explain that to me, I know nothing about motors.

thanks

**Rolf** · 17th May 2007 02:02 PM

Originally Posted by bitem2k

I recently salvaged an old windscreen wiper motor from a car.

The Motor has four terminals. Ive got two of them connected and it seems to work fine, is this right?

I intend to run the motor for hours at a time, and i would imagine that they are capable of that. I sometimes drive for hours in the rain and i would have my wipers on for the entire time.

If i run it for hours, it gets realy hot, and stays that way for about 30minutes after i turn it off. Is it meant to get that hot?

Thanks very much.

Depending on how old the car was that the wiper motor came out of, it could be a 6V motor.

**3v0** · 17th May 2007 02:23 PM

You need to figure out what each of the 4 wires do. It is possible that although you have it running it is not hooked up as intended.

When you turn a wiper motor off it runs long enough for the wipers to go back to the rest position. I think that means there is a always on wire to power the unit while it returns to the rest position. (1 wire)

In most cases there are at least two speeds. (2 wires)

Maybe a ground (1 wire)

Could also be that the motor is grounded through the case and you are using a wire for ground.

In the following page the author hooks an H-Bridge to one.

http://www.ayershome.org/~eric/robots/hbridge/index.shtml

**Nigel Goodwin** · 17th May 2007 02:34 PM

Wiper motors are pretty sturdy devices, they are often used in medium suzed robot project, and generally last extremely well, even when fed from 24V rather than their designed 12V. One problem with them is that they are only designed to rotate in one direction, and the brushes and bearings are designed accordingly.

**Andy1845c** · 17th May 2007 02:43 PM

Originally Posted by bitem2k

I recently salvaged an old windscreen wiper motor from a car.

Do you know if it was working when it was in the car? They are pretty tough, like Nigel said, but if it came out of a car thats been sitting for years maybe its rusty or gummed up inside. How does it feel when you spin it by hand? smooth and free or stiff and rough?

**bitem2k** · 17th May 2007 03:23 PM

thanks all for replies.
I took it out of my sisters car, the engine had died recently, the wipers functioned fine.

I cant really spin it by hand, its quite hard to move it. I thought that was because of some kind of internal gearbox?

The motor has a black 4 pin plug attached to it, going into this plug (from the motor) are two wires, red and yellow.

If i connect the first pin and the last pin, the motor spins quickly.

If i connect the last pin and the pin next to it, the motor turns slowly and in reverse direction.

Does this help?

thanks

**bitem2k** · 17th May 2007 03:24 PM

Originally Posted by Nigel Goodwin

Wiper motors are pretty sturdy devices, they are often used in medium suzed robot project, and generally last extremely well, even when fed from 24V rather than their designed 12V. One problem with them is that they are only designed to rotate in one direction, and the brushes and bearings are designed accordingly.

Nigel, do you think im running it the wrong way? Would that cause enough heat to fry an egg or even a nice juicy bit of steak?

**Nigel Goodwin** · 17th May 2007 03:38 PM

Yes, you can't turn it because of the internal gearbox - you should be connecting it so it runs fast, that's probably a direct connection to the motor. Usually one of the motor connections will be connected to the metal body of the motor, that should be the negative connection.

**bitem2k** · 17th May 2007 03:54 PM

If im connecting the motor up the wrong way round, ie (+ to -) and (- to +) opposite to which manufacturer intended,
do you think that would cause the heating?

thanks

**Nigel Goodwin** · 17th May 2007 04:25 PM

Originally Posted by bitem2k

If im connecting the motor up the wrong way round, ie (+ to -) and (- to +) opposite to which manufacturer intended,
do you think that would cause the heating?

Possibly, it's only intended to turn one way, try it the other way and see if it still gets hot - but electric motors DO get hot.

**bitem2k** · 17th May 2007 04:32 PM

by hot, do you mean HOT! or just hot.
thanks

**HarveyH42** · 17th May 2007 05:53 PM

Okay, 4 wires... You have 2 speeds, there is a 'Home' sensor so it doesn't stop in the middle of the windshield (windscreen), not sure if its one or two wires, almost all automotive ground to chasis. The gearhead in the one I took apart many years ago had a worm gear, so gotta go with the on direction deal. Put (-) to the case, and 2 of the 4 wires should make it go...

Since it got hot enough to mention, guessing very hot. I'd open the gear head and see if there is damage, and just to make sure its well greased after the melt. Makes a big difference...

**Nigel Goodwin** · 17th May 2007 06:11 PM

Originally Posted by bitem2k

by hot, do you mean HOT! or just hot.
thanks

I can't say I've ever had any occasion to feel a wiper motor!

But electric drill and vacuum cleaner motors get too hot to touch.

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