[AT] Semi OT - Trailer question

[Dudley Rupert]

John,
I certainly could be wrong but this sounds like maybe a short between the
tail light wire and the trailer brake wire either in the truck wiring or the
trailer wiring.
You might want to disconnect the truck/trailer connector, turn the truck
head/tail lights on, check the tail light pin in the truck half of the
connector for +12 volts (which, of course, you would expect to have) and
then check the brake pin to see if +12 volts were also present there.  If it
was this would, of course, indicate a short in the truck tail light/brake
wiring (I would not expect this short to cause any fuse to blow).
If there were no voltage present on the brake pin in the truck half of the
connector then you might want to do a continuity check between the tail
light pin and the brake pin in the trailer half of the connector.  If you
find low resistance here I would think that this would indicate a short
between these two wires somewhere in the trailer (again, I would not expect
this to cause any fuse to blow).
Let me hasten to say that I do not have a trailer with electric brakes so I
may be totally misunderstanding how they are wired up and this suggestion
may be worthless.
Dudley
Snohomish, Washington


-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of John Cullom
Sent: Tuesday, April 05, 2005 11:54 AM
To: Antique tractor email discussion group
Subject: [AT] Semi OT - Trailer question

Although I do use my trailer for hauling my engines & tractor - I hauled
out
my 16' flatbed trailer today in preparation for summer shows, & noticed
something peculiar. All the running lights work fine, as well as the
brake
lights, but when the lights are on, the electric brakes are engaging.
Enough
that when I turn the lights on when pulling it, I can really feel the
brakes
grabbing, so they are engaging all the way. Any ideas? I figured all the

grounds & other connections were clean & tight, since the lights worked.
But
could it be a frayed wire touching the body & feeding back into the
brake
wire? But that would blow the fuse, right? Got me stumped.
Thanks for the help,
John

PS - Should I check the grounds anyway Farmer?