Wiper motor only working on a single speed

[Duncan]

Hi I wonder if anybody might help me diagnose an issue with the wipers on our 1970 bus. Since we bought it a few months back only the slow speed works - switching to "fast" on the dash-mounted switch just stalls the motor in its cur rent position (switching off normally does park the wipers ok).
I've tested the black/yellow spade on the back of the switch, which I think is 53b (Fast speed terminal). That goes live on speed 2 as you'd expect, so I assume the switch and upstream wiring is ok?
Is there anything else I may have missed before assuming the 2nd winding in the motor is dead and replacing the wiper motor?
Many thanks
Duncan


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[Trikky2]

There isn't a second winding on the wiper motor. The slow speed is done by having a third brush on the commutator which is offset ie. not directly opposite the other. This is what makes the motor run slow.

Hence the likely source of your problem is a bad connection - or possibly a failed or stuck brush (though possible, I haven't actually ever seen this fault).

 

[DuncanF]

Thanks for your help Trikky. I removed the motor today and found that all the brushes are badly worn - only a couple of mm left - but the high speed brush was completely gone, with the copper wire burned away too and the spring out of its holder altogether.
I've never replaced brushes as a DIY job, but I found some on ebay of almost the right size for £7, so I'm going to give it a go before otherwise splashing out £87 on a new motor (that might not have exactly the same wiring either).
Fingers crossed!

 

[Trikky2]

Glad you found the problem. If the brushes you buy are slightly too big its no problem since they are soft and can be trimmed down both by scraping and sanding

Also clean up the commutator with some fine wet and dry to remove scratches and make it smooth or your new brushes will get chewed up quite quickly.

I guess your bus got driven in the rain a lot.

 

[Duncan]

Feeling very smug. Rebuilt the wiper motor today using my £7.00 eBay carbon brushes and it works a charm. Polished-up the commutator as suggested with some fine emery cloth, greased the internals (making sure the brushes were totally free from grease) soldered in new link wires and re-assembled. It worked perfectly first time. I replaced one of the spindles too (seized and still too stiff after a lot of effort), replaced the spindle seals & wiper blades and cleaned the screen with Rain-x.
£50 all-in and a huge difference.
Can't wait for it to rain!!


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[Trikky2]

Excellent job - well done

Love it when stuff gets fixed rather than just replaced. Feels great doesent it :mrgreen: