OK, without a doubt this is the easiest upgrade I have ever done on my shark. About the only thing that would be easier to upgrade would be from regular to premium fuel.
In a nutshell, the problem is this: When you switch to intermittent wiping on the main wipers(position 4 on the switch), the interval is controlled by the potentiometer on the lower right edge of the pod(2nd pic).
OK, this isn't exactly a high-priority problem, but what happens is you get the delay that was last set using that potentiometer... whether it was long or short. Also, I find myself constantly forgetting which direction to move the knob for more or less delay between wipes. And, by the time you're done fiddling to get the delay just right, conditions change and you've got to tweak it all over again.
Yeah, I know, it's not like it's the end of the world or anything. But check this out: For $40-$65, depending on whether you go to a dealer or an independent, you can swap your intermittent wiper relay for the VW/Audi part pictured below. It takes a total of about a minute to do so. You'll spend more time figuring out which relay to replace than you will actually making the change!
Well, OK, I'll help out a little bit... on my 78, it's the relay marked with "197" in the pic below.
The replacement part has one less pin on it -- the pin that goes to the potentiometer. This is fine, because the way the switch & relay are wired, you don't need that extra wire or the potentiometer because of the ingenious way that the delay is set with this relay.
The way it works is this: When you first put the wiper switch in the #4 position, the relay defaults to a 5 second delay.(Apparently this varies, as Alan stated 6 seconds and I found mine to be 5 sec.) Then, if you don't like the delay, for example 5 seconds is too often, you simply return the switch to the #0 position. When the windshield needs another wipe, flick the switch back to the #4 position. Now, whatever the interval was between the last two wipes(up to 30 sec.), becomes the new interval. Basically you show it what works and it repeats it. No more fumbling around, saying "I need a touch more delay" and finding that you can't see by the time the next wipe happens, or turning the potentiometer the wrong way and having your wipers drag on a dry windshield.
Big thanks to Alan Moore for bringing this mod to my attention in his fabulous "Porsche 928 Electrics" PDF, and in that document Alan extends his thanks to David Hendrickson who first proved that this swap works in the later cars. Now we know it works in the early cars too! Thanks guys!
