In general Vanagon alternators have a hard time waking up, on cold mornings especially. The problem is in the alternator itself, not the belt. The diodes that are the "on" switches for the output are sometimes a little (!) flakey, and a quick touch at the throttle will be enough to get the alternator "on line". It is the voltage regulator that is getting finicky, and will not always work as it should. My van has had this problem for the past three alternators in the last ten years. The tach has to go past 1400 RPM for my lights to go out.

  Low RPM at start-up can also contribute to the regulators' failure to start as it should. It can be a sign of impending failure of the alternator, or just a lazy regulator. The regulators are available seperately, from list vendors, and might be a good start, since that is lots cheaper than a new / rebuilt alternator.

  If the alternator output voltage is within spec (~ 14.0 Vdc when checked at the alternator) when the light is off, then don't worry too much. Just check your output every so often. Or better, install a voltmeter. And do keep an eye on the belt. Watch the second oil pressure sender and its wire, there at the back of the engine, hiding there by the crank pulley. If the wire is accidently knocked off, your low oil pressure buzzer will go off, even tho nothing is actually wrong except the wire.

Wayne Adamson <adamsonwd@TELUS.NET> wrote:
  Hello,I have been a member for about a year now and have enjoyed lurking and
have always been able to find answers in the archives if I needed.My van is
a 1991 2.1 waterboxer. The alternator light comes on,and stays on when I
start the van cold.If I rev it up I hear a click and the alternator light
goes out and the dash lights come on and all is fine until I start it cold
again.I thought it might be the alternator belt so I have tightened the
belt,but that didn't solve the problem?Last week I had a loud noise(like a
fan belt squeal) upon cold start-up,but that has only happened once,and
stopped after I revved it up. I have purchased all new belts and will change
them all this week-end,but I am not sure if this will fix the problem. I
will be driving the Rodgers pass this Xmas and really don't want a
electrical breakdown over the holidays. Thanks in advance..........this list
is great................
Wayne " The difference between an adventure and an ordeal is
attitude"(unknown)-2007A-21 KLR650(it's a manly Fire Engine Red)-1995
R100RT-1991VW Westy GL-ABC 6461 MOA-71007