The DIN circuit designation is 30 -- unswitched power, 87 -- switched
output, 86 -- control circuit positive, 85 -- control circuit negative.

Most relays don't care if you switch the function of 30/87 and 86/85.
However, some do.  The fridge relay in Westys is an example of both -- VAG
used 87 for input because that particular relay has two 87 terminals in
parallel, and they wanted to use the second one to piggyback the kitchen
supply.  But that same relay has a diode in series with the coil, so if you
hook 86/85 up backwards, it won't work.  This diode prevents the starter
from energizing the relay during starting.

If relay has a diode across 30/87 it must be hooked up so the diode is
reverse biased in operation.  Such a diode (or sometimes a resistor) is
there to reduce arcing/contact welding when switching inductive loads.

Yrs,
d

On Thu, May 11, 2017 at 1:16 PM, Neil N <musomuso@gmail.com> wrote:

> this is a LONG SHOT idea but most relays of this type have a diode or
> resistor or similar in parallel on switch side of relay. I REALLY
> doubt this comes into play here, but is polarity on switch side
> important in this application?
>
> If i recall, Vanagon relays typically use 85 for ground, 86 for positive.
>