Electrical gurus, I need help figuring out why my wipers (front & rear) do not work!

[gerlando]

It's getting close to the rainy season in Washington state so I cannot put off fixing my wipers for very long. My rear wiper has never worked for me and my front wipers recently stopped. They failed progressively though, the stalk controls stopped working first and a few weeks later the intermittent switch stopped working.

I'm "ok" with electrics and I have a Bentley manual and multimeter, but the wiring of the 911 has me confused. How can I test both the front and rear wiper systems to determine the point of failure?

Thanks in advance

[skrufy]

I assume you have done the obvious in checking the fuses, and you haven't said what year your 911 is.....

over the years I have found several fuses that look okay, but upon closer scrutiny, I found one of the contact ends of the fuze cracked thru and not carry any juice, even though it's not burned, etc.... you can also try checking your fuses for corrosion = same deal, not carrying any electrical power......

on my '77 930, the rear wiper would not work after having checked everything for voltage, etc...... the rear motor comes with a metal cover held in place by a metal hoop, kinda like the lid on an old mason jar or perhaps the oil filter on really old cars...

I moved the metal wire hoop out of the way, took the cover off, and found this really neat, simple electric motor whose design must be 50 years or more older.... what I then found was a tiny spring, maybe 10mm long, dangling from one side of the brush mounts for the commutator..... this tiny brush holds both brushes in the proper position.....picture this as a better visual: both of your arms are straight out front, you're trying to hold a basketball by your elbows, and a friend puts several rubber bands around your wrists to help hold the ball in place... your elbows are the brushes, and the rubber bands act as the spring to hold both haves together....

I reattached the spring to the other side- works like a champ

try that and see if that is the cause for the rear wiper not working.... careful with the metal cover, as it might hold the tiny spring if it fell off both halves.....

hope this helps, at least with the rear wiper..... good luck..

Tim
Alpine, Az

[gerlando]

Well I took apart the rear wiper motor yesterday. The original gear oil had the consistency of gummy candy. I re-oiled it, put it back together and double checked my Bentley manual to find that the motor had been wired incorrectly! Once I put the wires back on it motor ran for a bit, then got stuck. I moved the magnetic spindle a bit and it worked for another minute or so before dying again. It appears to not be able to overcome the resistance of the plastic "ramp" on the main internal gear that causes the switch to flip. It seems like the motor's fried. :-\

[spuggy]

Originally Posted by gerlando

It's getting close to the rainy season in Washington state so I cannot put off fixing my wipers for very long. My rear wiper has never worked for me

I've never had a rear wiper, and never really felt the need for one, even daily driving in WA. With any speed, the rear clears itself, and the factory delete plug replaces a disproportionate amount of weight precisely where you don't want it on a 911 - high up, and in the rear.

Your choice though

and my front wipers recently stopped. They failed progressively though, the stalk controls stopped working first and a few weeks later the intermittent switch stopped working.

Ah, now. I've never managed to get my intermittent wipe working despite several attempts, although I do know it relies upon the internal switches in the wiper stalk for correct function. It might just be the stalk that has killed the intermittent function.

There are a few threads on here regarding cleaning up and re-setting the wiper stalk reed switches to make them operate correctly. The reed contacts are very small, carry a relatively large amount of current, and get bent out of correct alignment over time.

On mine, the actual action of the switch itself was so shot (250,000+ miles on the tub) that I opted to replace the stalk after looking at the reeds themselves with a view to re-setting them.

I mourned the 70's graphics on the stalk for about a week, but the crisp, positive action of a new switch mechanism was a revelation - a joy to use.

Good luck!