At 11:52 PM 3/10/2003, Myron Lind wrote:
>My 1982 diesel had a factory looking blue wire (appears to be from the
>alternator) and then the other side of the coil for the relay was grounded
>on the screw that held the relay. This would also be off during starting of
>the van, but would connect the batteries if the key is in the "on" position,
>correct?

No, the blue wire goes to the D+ alternator terminal which feeds/is fed by
the alternator light and a resistor paralleled with it.  If the alternator
light is lit it means that the D+ terminal is at least two volts (and
likely more) below battery voltage, or that there's a high-resistance
connection somewhere between D+ and the light.

What's supposed to happen is that when the Alt is not charging, D+ is low
and acts as a ground for the light.  At the same time the light and
resistor feed some current into D+ to tickle the Alt and get it to start
charging.  When it does begin to charge, D+ comes up to charging voltage
and the light goes out since it has about the same voltage on each
side.  Also the fridge relay kicks in, since it now has charging voltage
from D+ on one side and ground through the start solenoid on the other.

>I thought it would be better to go with terminal 50 since that won't
>activate the relay until the alternator is charging (that is how my 83
>waterboxer worked--I could hear the relay as I revved the engine and saw the
>headlights brighten), and I hooked up a second relay (no need to debate the
>relay/isolator--that's not what the question is about) to charge a second
>battery. I brought a wire from terminal 50 on the emergency brake light
>switch back under the seat to the relay. Now the original relay runs the
>fridge and the second relay. The second relay allows the second battery to
>be charged once they both kick in.

Suggest you unhook the second relay drive connection (85 or 86
terminal).  If everything (else) including the ALT light now is ok, hook it
up again so that the battery relay gets its drive from the fridge relay 87
terminal instead of direct from D+.

If that doesn't cure it, suspect one or more bad diodes in the Alt. D+
circuit, or a corroded connection giving high resistance.

david

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"