Autocheck follies

[Mike Arman]

The autocheck unit contains a pair of current sensors, and as long as both
head or tail lights are drawing the same amount of current, autocheck is happy.

If one bulb goes out, the autocheck detects the imbalance, and complains.
It turns out to be pretty low-tech - a couple of (bimetallic?) flat plates,
which appear to flex when the current is imbalanced.

If you relay the headlights, you need to draw the same amount of current on
each wire - it doesn't matter if the relay current is much smaller than the
bulb current, just as long as the two match autocheck is happy.

Same thing with tail lights - the problem with adding a trailer socket is
that we tend to pull the US-style single-wire-works-both-brake-lights off
ONE of the Audi brake light wires, and autocheck detects the imbalance. The
other problem is that the Audi wires are very small, just barely adequate
to light up the stock brake and tail lights, and when we add extra loads
for the trailer lights, things tend to go poof, all the smoke comes out,
and you've just toasted parts of your wiring harness.


Best Regards,

Mike Arman