Re: [T3] DBB alternator related subject

[Jens Vagelpohl <jens@type4.org>]

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On Mar 25, 2005, at 4:29, Jim Adney wrote:

> On 24 Mar 2005 at 17:21, BOB2TYPE3S@aol.com wrote:
>
> > Russ, where would you find the battery relay? Would this be something 
> > you
> > could "borrow" from a water cooled VW? Or could one use the rear 
> > window defogger
> > relay? Thanks.
>
> I got to wondering if the diagram was actually showing a second VR, 
> with just
> the cutout relay used. Note that the diagram shows 2 coils in this 
> relay, which
> makes it a very special relay. The VR, however, comes with 2 coils, so 
> maybe
> they're just hooking up a second one and using part of it.

After a little digging I found a supplementary current flow diagram for 
the VW 412 from August 1972 that shows a second battery. Unfortunately 
I don't have a scanner here, but I'll try to describe it.

The second battery has a normal ground strap, just like the first. From 
the positive post there are two leads, one (2.5 mm, red) going to a 
connector in the engine compartment. The other one (4 mm, red) goes to 
a simple battery cut-off relay (connection numbered 87). When it is 
switched on, the battery current flows out the relay connection 30 to 
the fuse box for distribution (6 mm, red/white).

The cut-off relay port 86 has a lead (blue, 0.5 mm) that ends in a 
connector under the dash, which hooks it into the circuit that powers 
the generator light in the instrument panel and originates at the 
voltage regulator D+ connector. The cut-off relay connection 85 shows a 
lead (0.5 mm, blue/red) going to the starter inhibitor/reverse light 
switch at the gearshift selector (automatic trans, of course) at 
connector 50A, joining a lead (4 mm, red) from the same connector to 
connector 50 on the starter.

So the cut-off relay is a run-of-the-mill relay, just a bit sturdier 
because it carries the full battery output from the second battery.

jens

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