On Thu, 14 Feb 2008 22:39:57 -0500, "NokNokMan"
wrote:

Hi all,
I'm just about finished building my utility coal-hauler trailer. (Metal
content? about 300lbs. angle-iron and half an 8" spool MIG wire). Since
this trailer has a GVW of 3500Lbs., brakes are required. I had trouble
determining if a breakaway kit was needed, but all signs pointed to "yes".
So if the hitch somehow falls off and the safety chains fail and I hit lotto
and get struck by lightning, then the breakaway battery will supposedly
energize the actuating magnets in the brakes.

It will IF they get triggered. You MUST provide a 'bomb-proof' (for
the expected load of pulling that lanyard before failure) and totally
independent anchor point for that break-away lanyard that won't get
tangled up in the coupler. I put a 1/4" eye bolt through the body or
the pickup bed near centerline and/or the license plate, with fender
washer backups.

For a passenger car with a center license plate, you could use the
eye bolt as one of the license plate bolts, too,

And make sure the hook on the vehicle end of that breakaway lanyard
has a locking gate or bail, not an open S-hook that can fall off the
anchor way too easily.

DO NOT clip the lanyard to the bumper hitch or the receiver hitch,
because if the welds/bolts holding the hitch to the chassis fail, so
does the lanyard anchor point. If the whole thing falls off (lousy
welds...) the lanyard never trips - except by chance, getting snagged.

My question is this: if I
were to attach everything to my 7-connector wiring connector on the back of
the truck (one wire is for the electric brakes which are connected to a
dash-mounted brake controller) would I fry said controller if I should
happen to yank the lanyard out of the breakaway switch? Assuming that
happened, the twelve volts from the breakaway battery would energize not
only the brakes, but the 12v out from the brake controller itself.

The standard way of wiring the break-away switch would backfeed to
the car if tripped while still coupled - So what? The controllers
should deal with it gracefully. If it only took that to blow it up,
there is a serious design problem in the controller.

I know
the manual says "don't wire this thing up wrong or you'll ruin it". I'm
wondering if a diode between the controller and the breakaway unit would
stop the current from flowing to the controller. If so, what kind? I have
no clue about this sort of thing. Would the diode affect the operation of
the controller? Any help would be much appreciated.

Don't try getting inventive with safety systems without doing some
serious research - which you aren't getting over the internet, except
to guide you to more definitive sources of information. There are too
many people here that throw out guesses and conjecture without plainly
labeling them as such, and not all of them get called on it.

You don't need diodes or any other mods not specifically authorized
by the controller maker.

-- Bruce --