|What's that missing wire? The functions of all the others are obvious.|
The first thing I did was to begin some research online, and I found many references to similar problems, with an equal number of references to suspicious windshield wiper switches as being the probable culprits. Getting the switch out was a straightforward operation once the steering wheel was off, along with sundry other bits of the steering column, and when I removed it a piece fell out from the middle of the switch. Aha!
A small bit had broken off (plastic . . .) from the portion of the wiper switch mechanism that controlled the windshield washer function. That little piece coaxed the switch to stop squirting when you released the lever, which you pull toward you to pump washer fluid onto the windshield and its bugs. Why should this have anything to do with the wipers turning themselves on? Well, it was broken and not all there anymore, so I figured I had to replace the switch in any case, whether or not this had an influence on the wipers turning themselves on, so I went back online to order a new one.
My car is a '74. Evidently, the switches for the 1974 and '75 cars differed in some way from all other such switches, whether before, or after those years. A switch for the '74 model is NLA. Things that are no-longer-available immediately skyrocket in price if anyone has a new-old-stock example in their possession, because even an odd part like this has a market for it somewhere in the world. But, the prices didn't go up, because there simply weren't any to be had, so there was nothing to raise the price on. Grrr, again.
Of course there are used switches to be found from the Porsche recyclers, but why would I want another 40 year old plastic switch that was likely to self-destruct several minutes after I installed it? One guy I sometimes communicate with, who lives a few hours away as the Porsche flies, has been rebuilding old Porsches for 25 years, and he told me that he has more than twenty old switches like this on hand, but he was too busy to sort through all of them to see if any of their part numbers matched mine. Hmm, it would take a full day to drive there and back, what with chatting and all, only to find, possibly, that he had no matching switch, and all of them were ~40 years old, so I didn't take that drive.
|The new switch is the fatter one with a picture, not text.|
He knows plenty of stuff about old Porsches, but he won't tell you all of it, because what he knows equals his bread and butter, so I had to discover the following on my own: The difference between a 1974 switch and a 1976+ switch is the fact that there is a different picture on the end of the stalk, and the stalk is made of plastic (!) instead of metal. Otherwise, the wiring is identical. I further discovered that my turn signal switch/arm had already been replaced at an earlier date, and it matched the design and material of the new wiper switch that I bought. Serendipity. I now have two matching switch stalks. Is that all there is to the difference between the NLA '74-'75 switch stalk and a newer one? In a word, yes. That, and they threw in an extra brown ground wire with the new switch, one that has female spade connectors on the ends of it, because the later switches have intermittent wiper function for which this is required, whereas the intermittent function was optional with the earlier models.
|One of a number of ground clusters on my car.|
In another feat of engineering brilliance, Porsche built these midyear cars with the relay controlling the wiper motor positioned inside of the dashboard, instead of adjacent to the block of fuses in the trunk. You can't get at those relays if they fail, unless you remove all the heating and ventilation ducts and controls from the trunk, along with the air plenum, and other bits. Never mind that simple business, on my car the relay is built into the wiper motor itself, so it's necessary to remove the instruments, reach your arms through the resultant holes in the dash, and fiddle with the relay blindly, no tools allowed. You can't get the relay out this way, you can just fiddle with it, but that's what it took to get my wipers working again (courtesy of my Porsche guy), not the replacement of the switch, so I didn't need to buy it in the first place, but now it matches the turn signal lever at least. How long the relay will continue to work is anybody's guess, and it will be necessary to take half of the car apart when it fails again and sends my wipers into a frenzy.
|The wiper motor as seen through the speedo hole.|
To be continued if I figure out what the missing wire is in the picture at the top. I'll need to consume extra protein to do it.