Trailer Wiring

[Curt Sprenger]

Revised Trailer Receptacle wiring write up.

Contributed by Curt Sprenger on 10.20.2008

Revision One, revised
10.21.2008:

Revision One takes out the BK relay and the 12V relay. I
hooked up the trailer to the bus this afternoon. The discovery is the relay (BK
relay) comes out of the mixture. Greg O'Connor is correct...the trailer brake controller
will not function correctly with a relay. The trailer brake controller wire should
be wired only through the fuse block, allowing variable voltage to the trailer
brakes. The new Tekonsha Prodigy brake controller is working fine after this
change.

Wire the 12V the same...no relay and through the fuse block. CRS (and
DUMB too) on my part.

The following doc. Is revised to reflect the above
changes.

End of Revision
One.

Before I begin...It's a good idea to sketch out on paper a
new panel as described later, the bus trailer receptacle, a new wire loom, and
a new brake controller.



I've pretty much finished the bus Trailer Wiring project. Just need to tidy up
a bit. All is working from what I can tell. I need to hook the trailer to the
bus to validate the new trailer brake controller. The controller's display
shows it's not hooked up to the bus which is true.



What I did...An 80' loom was made (6 wires, allowing for future wiring
needs…overkill, but easier to do now than again later). I thought 80' that was too
much wire...ended up using all but 2'. It took a day to install the wire
loom...that counts my buddies stopping to talk. The loom is made using #14 wire.
The loom is inside 5/8" split loom. #16 or #18 wire will work, and will
make it easier to install the smaller diameter loom. The loom wires are used to
trigger the relay # 85 pins (turn them on), and then wire the relay output #
87using larger size wire to the trailer 7 pin receptacle.



I also made up a panel consisting of....6 relays, an 8 gang fuse block, one 30
amp circuit breaker (CB), and a ground lug. I labeled the relays L, LT, RT, SP,
SP, BU. The SP means Spare Relay. The relay ground pins # 86 are wired to the
ground lug on the new panel.

The CB is wired and provides power to the 8 gang fuse block. The other side of
the 8 gang fuse block, one each, is wired to a # 30 relay pin.



The original trailer receptacle wires ...3 wires were used. Testing them showed
they are OK. The wires are the Lights (L), Left Turn (LT), Right Turn (RT). Two
other wires did not show any power. One could have been a ground wire. The
three wires were wired to trigger the L, LT, RT (new) relay # 85 pins.



Two new loom wires were used to send power to the rear of the coach. The wires are
the brake controller brake wire from the new brake controller, and a back-up
wire. The brake controller wire is wired to the #7 position of the fuse block.
The trailer receptacle wire is wired out the fused side of #7. The back-up wire
is connected to the Back-Up pole on the gen compartment 12V panel, and at the
rear to #85 of the BU relay.



The brake controller exciter signal is wired to the Stop Light pole on the gen
compartment 12V panel. Power for the brake controller is taken from a CB out
front of the driver. And the ground is connected out front as well.



Power (12V) to the panel is supplied from the battery collection lug (isolator)
to the input side of the 30 amp CB. The CB output (AUX) side supplies the power
(12v) feeds to the #1, 2, 3, 4, 5, 6, and #8 position on the fuse block. The
fused side of # 8 is wired to the trailer receptacle 12V pin. Complete
all other wiring before doing this step.




The relay # 87 wires to the trailer receptacle...The 4 are # 12 wire. The BK and 12V from the fuse
block to the trailer receptacle are # 10, but that is what I originally used
(before testing/changing), #12 would be fine.



The only real issue is routing the new wire loom. The rest is easier than it
sounds. I'm getting ready for the Buellton, CA rally and for now do not
have the time to make up a schematic.



Our coach has dual (each side) red led tail/brake/turn/flasher LED lights.



With the brake applied along with an L or R turn, the turn side blinks, the
other side is a steady brake light.

On Tue, Oct 21, 2008 at 4:42 PM, Curt Sprenger <"curtsprenger@gmail.com"> wrote:

Greg,

You are absolutely correct. Use no relay for the trailer brakes. I've changed the brake wiring and all is fine, and will change my write up and republish it. The 12V relay also comes out of the mix. I'll cover that in my write up as well.

On Tue, Oct 21, 2008 at 3:29 PM, Gregory OConnor <"Gregoryoc@aol.com"> wrote:

Is BK Brake or stop light? I dont think you van transulate the

variable voltage from the Brake controller thru a relay. 3 volts in is

12 volts out.

Greg94ptca

--

Curt Sprenger
1987 PT38 8V92 "MacAttack Racing"
Anaheim Hills, CA

--
Curt Sprenger
1987 PT38 8V92 "MacAttack Racing"
Anaheim Hills, CA