Agreed, this has been an interesting thread with a lot of good information. BTW, a common failure on (I'm going to say earlier, but we're talking 80's and later) VWs is the inline spade connector to the solenoid. Corrosion builds in that connector resulting in a high resistance joint. This got me on my Cabriolet (an 88) a few years ago. Someone here pointed out what the likely problem was and he was correct. Because the solenoid does draw a lot more current than one realizes any resistance is a big problem.