Bill,
There could be several reasons why the isolator on your 90 vanagon
did not work. But one thing is for sure, the vanagon alternator does
put out plenty of power to make them work.
I get 13.8 volts with lights off.
First the mechanic told you he knew what he was doing.
Later he tells you the vanagon alt. does not put out enough power.
Hmmm...if he knew that, why did he try the installation in
the first place?
I am just guessing, but maybe the reason your installation didn't work:
The mechanic used the wrong isolator. There are many different models
for different cars, made by the same company. They all look the same.
Nobody ever has the two models for the VW in stock. Always had to
order them.
(First everybody tries to talk you into something for a ford or chevy
etc.).
Or maybe the isolator was defective. Or the tab on the regulator still
made contact. All I can say is, the installation works on my westy.
I used the SurePower isolator on vanagon campers for 14 years.

The reason that I use the isolator and not the little relay under
the seat is that I don't want to risk overheating the wiring
going from under the dash to the relay. (imho)
Harald
90 westy

Bill wrote:
> About a year ago I went to the expense of having a mechanic with an
> impressive German accent install a solid state battery isolator. It may
have
> been a SurePower; I'm not sure. It was blue with fins and four connecting
> terminals on it. It was definitely the one that was listed by the company
> for the Vanagon. Even though  the mechanic said he knew how to hook it up
> and had done it before, he could not get the isolator to work properly.
He
> even called the isolator tech support number and their suggestions didn't
> work either. I think the problem turned out to be that the Vanagon
> alternators just don't put out quite enough power to make the solid state
> isolator work properly.