Towed vehicle charge line kit
part number 156-25
Time Tested • Time Proven
Installation instructions
All specifications are subject to change without notice.
855407-01 11.17
6110 NE 127th Ave.
Vancouver, WA 98682
Read all instructions before installing or
operating this device. Failure to understand
how to properly install or operate the charge
line kit could result in extensive property
This kit requires…
• …a 6-wire (or a 6- wire to 7-wire) power cord between the
two vehicles with matching sockets; and
• …an RV charge line kit similar in function to this kit in the
motorhome. If a charge line isn’t already present in the RV,
order part number 156-75, the motorhome charge line kit.
Installation instructions
1. Attach the included length of red 14 gauge wire to the
center pin (the number 2 pin in Figure 1) in the towed vehicle’s
power cord socket.
Apply a silicone sealant to the socket terminals where the
wires are connected; makecertain that all electrical connections
in the socket are watertight.
If the socket terminals aren’t sealed, stray voltage may
energize the turn signal wiring. This will, in turn, activate
any devices controlled by the turn signal wiring. Roadmaster manufactures two supplemental braking systems
(InvisiBrake and the 9700) which are so activated. Stray
voltage may also cause inadvertent activation of any other
device so activated. In the case of supplemental braking
systems, severe brake system damage, loss of vehicular
control and other consequential damage may occur.
2. Route the wire to the towed vehicle’s battery, or if the battery isn’t in the engine compartment, to the positive battery post
in the engine compartment. Choose a route that will avoid the
possibility of a short circuit or other damage to the vehicle.
Cover the wiring along its entire length with the included
Fax: 360-735-9300
split loom.
Route all wiring to avoid moving parts, sharp edges, the
fuel lines or hot components such as the engine or exhaust
systems. Use the included wire tires to secure the wiring
out of the way.
Wiring exposed by moving parts, sharp edges or hot
components may cause a short circuit, which can result in
damage to the vehicle’s electrical system as well as other,
consequential damage.
Wiring which is attached in close proximity to the fuel
lines may ignite the fuel.
Failure to follow these instructions may cause property
damage, personal injury or even death.
3. Find a suitable mounting location for the included circuit
breaker — it must be mounted on a flat surface, within approximately 6" of the vehicle’s battery (the closer the better), at a point
where it will not interfere with the operation of any components.
Using the two included self-tapping screws, attach the
circuit breaker.
4. Route the red 14 gauge wire to the circuit breaker and cut
it. Strip ¼" of insulation from the end of the wire and crimp it
onto one of the #10 ring terminals.
5. Attach the terminal to the gold post on the circuit breaker
(identified as ‘BAT’) with one of the included nuts.
6. Attach one end of the remaining length of red 14 gauge
wire to the silver post on the circuit breaker (identified as ‘AUX’)
in the identical manner.
Route this wire to the positive post and cut to length.
continued on next page
Figure 1
Once charge line kits are installed in both the motorhome
and towed vehicle, they will help maintain the vehicle’s battery charge while in tow, supplying up to 15 amps of current
to the battery.
Required tools
• wire crimper
• side cutters
• volt meter or test light
NumberColor Towed Vehicle
1........... Blue............Brake monitor light
(electric trailer brakes)
2........... Black..........Auxiliary/Charge
3........... Green.........Right Turn/Stop
4........... Brown.........Taillights
5........... White..........Ground
6........... Yellow.........Left Turn/Stop
continued from preceding page
If helpful, you may use the included 5/16” ring terminal to
attach it. The vehicle’s engine must be off when you attach the
wire to the post.
7. Ensure that a good ground exists between the frame of
the towing vehicle and the frame of the towed vehicle.
Note: to confirm that the charge line is functioning…
• With the charge line connected from the motorhome to
the towed vehicle and the motorhome engine running, disconnect the red wire from the towed vehicle’s positive battery post.
• Connect a volt meter or test light from the red wire to
the towed vehicle’s ground.
• If the volt meter or test light indicates 12 VDC+, the
charge line is functioning.
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