Electrical Troubleshooting
 

I have had no park position or pulse wipers for as long as I have owned my 79 911SC and decided today to fix it.

Armed with my Bentley Manual I began with the wiper motor. Looking at the schematic drawing I expected to find no power at terminal 53a. That terminal should be hot whenever the key is on. The wire was hot as it should be so I checked the park switch and found it working OK. It closes when the motor is not in the park position and energizes terminal 53c (Blue/White)
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From there I went to the pulse wiper relay and checked the wiring. The Blue/White wire is connected directly from the wiper motor to the pulse relay and I found power at that terminal. The Red/White wire is powered with the key and it was also OK. The Blue wire was hot when the plug was connected to the pulse relay and was not when the connector was removed. This is also consistent with what the Bentley Manual described.
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After this I removed the steering wheel and wiper switch to check for power. The Blue wire is connected to the pulse relay and it had power at the wiper switch. The adjacent black wire had no power so I check the contacts and found no connection. After adjusting the contacts the wipers parked properly and the intermittent control also worked. It is important that the contacts are open when the wipers are switched on and closed when the wipers are switched off.
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I don’t know if this repair will last but I know that if it doesn’t I can always get a new wiper switch from our host.

Ross

Nice work. Thanks for the writeup.

Thanks for the write up and photos. Excellent detail.

yes,.....good stuff....thanx!

Best,

Doyle

I found this tread while during a search.. Good information here for what seems to be a common problem with our cars, so I brought it to the top..

Yeah, I too ran across this an want to bump it up, subscribe and post this diagram from my Haynes for future reference on the topic. - Rich

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