Wiper Motor Inspection

Hello All,

Took my wiper motor apart to have a look inside recently - aside from a lot of old grease it looked OK mechanically, but I'm less of an expert on the electrical side of things. Some advice on whether this stuff looks knackered or not would be very welcome! Thanks in advance!



How much wear is acceptable on the brushes? I will probably replace anyway whilst I've got it apart


This magnet is cracked - I can see how it was done, as the rotor gets pulled about by the magnets as you try to refit it. Is this a showstopper - any idea where I might get a replacement?

Where's the ball bearing out of the end of the shaft?
If it rotates when switched on it's ok. If not your after a new one. They do sell them but not cheaply. I did a little wright up on the motor in the technical section but photobucket has put a stop to that.
Don't try and force it back together as the brushes won't go passed the commutator and you'll smash them. They have to be eased over it by fitting the motor first then putting the cover on last.
Replace the long bolts loosely at first then wire it up and run it whilst tightening the long bolts or the cover may snag the workings. You can twist it a bit to get the seating bang on if it is causing problems.

The motor looks ok but you can't tell visually if the is a short in the windings, although that is unlikely. The brushes look ok too so long as they make contact and their is still some Spring pressure in them when fitted. I can't see the cracked magnet stopping it from working to be honest but it may just affect its performance enough to stop it from starting.

Col

Thanks gents - sound advice and some great tips from Bobsticle. Sounds like the first thing I need to do is put it back together (kind of) and see if it works! I'll let you know how I get on.

You can test the windings for continuity quite easily if you have a multi-meter. Set the meter to continuity test, the one that goes beeeeeep when you touch the probes together, then touch one probe to one of the copper segments and then work you way around the rest of them with the other probe you should get a beeeep when you find the other end. once you get a beep move the stationary probe one segment and repeat the process, if you don't get a beep on any of the windings then its buggered. The broken magnet shouldn't be a problem but the brushes look to be on the limit so I would replace them.

What about if it beeps whatever you do?! Suggests a short somewhere in the windings I guess..

indeed

So now I'm confused - just put it back together and gave it 12v and it spins quite happily; drew about 1A.

Is all well, or is it just because there's no load on it?

I can only assume that I did a poor job of measuring the resistance between the commutator segments - or fundamentally misunderstood how it works.

Barney

The static resistance on the windings will only be a few ohms, low enough for the continuity tester to beep. Once it spins the inductance goes up and limits the current draw. Thats why is doesn't burn out so long as its spins and why it does real fast if you use it when the wipers are stuck. Remember its just about 2 ft of copper wound in a coil so its resistance will be an 1 or 2 ohms when its static. I'm intriuged by the broken magnet, it must form new N/S poles at the crack if it is 2 pieces yet it seems OK, best not to wonder?

rob1miles said:

The static resistance on the windings will only be a few ohms, low enough for the continuity tester to beep. Once it spins the inductance goes up and limits the current draw. Thats why is doesn't burn out so long as its spins and why it does real fast if you use it when the wipers are stuck. Remember its just about 2 ft of copper wound in a coil so its resistance will be an 1 or 2 ohms when its static. I'm intriuged by the broken magnet, it must form new N/S poles at the crack if it is 2 pieces yet it seems OK, best not to wonder?

Click to expand...

Gaffer tape

I suspect I will damage something if I try and replace the magnet, but actually getting back to it if I need to at some point in the future is only a few hours work, so I will leave it be.

New brushes and back together with a clean and fresh grease it is.

Can anyone recommend a source for bushes to fit this motor? Or what to ask for?

Single speed brush set and plate.

I haven't bought one as my motor is a two speed and has a third brush.