trailer wiring - be careful here!

[James Marriott]

> The answer, therefore, is going to involve some relays, and a
separate hot
> lead, run from the battery (and properly fused) to power the
trailer
> lights. The resistance of each relay coil can be about 300
ohms, which at
> 12 volts will draw 40 milliamps or one half a watt (which
hopefully will
> remain within the capacity of the wiring).
>
> We'll need a relay to work the brake lights, a relay to work
the parking
> lights, and a pair of relays to work the turn signals. Which
immediately
> brings us to another gotcha: Wiring the turn signal and brake
light relays
> in parallel will make the turn signal filament burn steadily
when the
> brakes are on, and wiring them separately will make the
trailer's turn
> signal flash in reverse to the car's signal. (car on, trailer
off, trailer
> on, car off.)
>
> Two tentative solutions to this new problem are, one, do the
relays and use
> them to feed the $15 converter box, or two, use lights on the
trailer which
> have separate brake and turn signal bulbs!
>
>
> I'm not yet sure exactly how I'll work this out, but when I do
(next few
> weeks, time permitting), I'll post a schematic which will solve
this
> problem once and for all.

This problem has already been solved for $40 at any parts store.
It is a combination of the $15 4/3-filament converter and a
separate power supply wire (on the t44s available handily from
the nearby battery).

cu, James Marriott
'87 4kq (alias "late-B2 90q") with rare NG engine, 181k, hitch
'89 200q (MC1, ProconTen/no bag, 1.8 blah blah), 132k, hitch
Boise, ID, USA     http://www.webpak.net/~marriott/