Have you tried jumping the D terminal to B+ to see what happens?? That would rule out anything with the alt such as a funky regulator or something.. My bet would be, though, the low voltage at the D terminal is your culprit.. I had similar issue with one of my MK1's years ago..
Never tracked down the real problem though.. The car was junk and I'm kinda lazy so I ran a switched B+ to a light socket with a 194 bulb duct taped to the dash, then from the socket to the D term...
Yep, that is what inspired "thought" in first place. Temporally hooked small jumper lead from D+ to Pos on Batt, instant excite at start and kept up 14.3 voltage at idle when removed. New-ish thought, since starter has a terminal to feed ign while starting (on the diesel starter of all things) run a wire thu diode to D+ from there.
Voltage drop in Alt LED circuit....2 volts for the LED, aprox. 9 volts at the 470 ohm LED resister (keeps the 12v from frying the LEDs), and who know on the big (1 watt) resister. And I have 4.8 volts at the D+ term with key on, engine not running. I hate math.
Sweet! Did you try a regular bulb yet? I was thinking about rewiring the light bulb so it would not interfere with the current flow to the alt excitation.
Not sure how to install one, the LED plugs into the (wonderfull) Circuit Board using it's leads into clips molded into the Circuit Board.
Hard to change that to a lamp setup. And I wonder if there is some reason that VW used a LED any-way, as a diode to seperate circuits?
I suspected it was just for longevity.. I bulb usually doesn;t last as long as an LED, and on that paticular setup, if the bulb blows it stops charging with no indication to the driver..
Not sure how to install one, the LED plugs into the (wonderfull) Circuit Board using it's leads into clips molded into the Circuit Board.
Hard to change that to a lamp setup. And I wonder if there is some reason that VW used a LED any-way, as a diode to seperate circuits?
Ohhhh, what car are you working on? I was talking about my A1. It would be nice to be able to check the volt drop on a good working one.
This would be the DumBuny, 1984 GTI Sport (ish).
