Neil, if the fridge relay you just added is using the blue wire it might
now mask the problem of engine run-on since it would be an additional
load on the circuit like the brake bulb was. The run-on problem may
disappear or occur less frequently now but it is not solved by this
either way.

Looking at the various years diagrams in the Bentley I see they added a
diode to the blue wire circuit of the instrument cluster beginning in
1985. They would have done this to prevent the type of problem you are
having. If the existing black wire won't carry the load in place of the
added relay you could just add the diode and keep the relay. The diode
blocks the alternator D+ from providing reverse current flow to the
black wire circuit of the ignition switch after the switch is off.

I always upgrade my earlier vans to tachometer clusters or I would have
likely run into this problem before myself.

Mark

neil N wrote:
> Mark.
>
> Awesome info and great suggestions.
>
> I just added a fridge relay downstream of the aux battery relay. It
> would have been there in the stock configuration and if I keep my
> Dometic 182B (dang thing still goes out randomly!) I would hook up the
> 12V eventually. Regardless...... I'm sure you're right. The added
> relay is likely staying closed. This makes the most sense.
>
> The detail about the added relay was something I'm not sure I posted
> when originally asking this question.
>
> The good news is that I know the exact route to drive to get it to
> malfunction. I will do this. If the problem still exists, I will do as
> you say. I wasn't sure if pulling the blue wire with engine running
> would do harm. Good to know I can pull it with engine running to test
> things.
>
> I checked for voltage (drops?) at grounds on "stars" above the fuse
> box. Nothing there. And no voltage when measured at the brake warning
> light ground(s).
>
> I too had thought to run a heavier gauge wire from the ignition switch
> so the wiring remained stock, but it would be good practice to learn
> how to measure current flow and see (thank you internet) if the
> existing wire is sufficient.
>
> And thanks for explaining so well, what I was just starting to
> understand. I figured the load of the brake warning light was the
> reason. Just didn't know exactly why.
>
> Again, really appreciate the direction/explanations.
>
> I'll post what happens to the list, along with some droll info about
> solving the poor acceleration/power issues I was having, soon.
>
> Cheers,
>
> Neil.
>