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On 16 Apr 2003 at 17:23, Ben Doughney wrote: > on 16/4/2003 2:09 PM, Jim Adney at jadney@vwtype3.org wrote: > > > Personally, I > > have never seen a VR fail such that it gave high voltage. OTOH, if you had a > > short to ground of the DF wire, between the generator and the VR, this would > > alco cause this problem. Take a good look at your wiring harness and make sure > > that it has not been damaged or that you don't have some body panels coming > > loose and cutting into it. > > I thought it was strange too, since it was working fine and then suddenly > went high. I put it back in again after I had finished putting that new > generator in and was sure the rest of the system was working, and the old > regulator was still putting out a high voltage. I presume the bad generator > damaged it in some way. When your D+ wire came off the VR just sensed that there was no output and turned the field current on full blast in an attempt to get something out of the generator. This eventually burned up the field windings in the generator. This could then have burned or welded the relay contacts in the VR. > One interesting thing about that regulator though, is it doesn't have the > wire wound variode on the bottom, it has a two plate thing which I presume > is made out of some special metal to do the same thing as the wire wound one > does? That's not the Variode, that's just a resistor. I haven't seen that version of it, but that resistor is a weak link in the VR design. It has a resistance equal to that of the field winding and it causes the field current to fall to a value of 1/2 of it's max, so that the field current can have 3 possible values: zero, 1/2max and max. This gives a little better regulation than zero and max. The Variode is just a diode, which has a non linear resistance curve. The originals came with an odd little diode in a copper colored case soldered on the underside, but lately there has just been a wire there and a much more modern looking diode mounted inside. > The plus side of all of this is I think I understand how the charging system > works a lot better now! ;-) It's a great feeling, better than money in the bank! ;-) -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org