Trailer Brake Controller
Installation (Range Rover III/L322/LM)
Introduction
Choice
of Controller
Mounting the Controller
Wiring Connections Needed
Access Behind the Dash
Power Supply and Ground Lines
Brake Switch Sense Line
Controller Output Line
Reassembly Tips
Parts & Sources
More Information
Photo at right:
Brake controller mounted in position on the lower dash
Introduction
For heavy trailers, as mentioned on the main RR
III towing page, you need provision for controlling the trailer's
brakes, which in the
US are usually electric. Unfortunately, the new Range Rover III wiring
kit (see RR III Trailer Wiring Harness
Installation Page) still has NO PROVISION for this. The blue brake
wire is connected to the (Ford branded) 7 pin plug, but the
instructions
say "not used". Ironically, Land Rover's corporate parent (Ford) leads
the industry in trailer brake wiring, with some new models actually
having a factory trailer brake
controller buiilt in. I don't expect Land Rover to be that advanced,
but it would be nice if they could at least catch up with Chevy and
spend the extra $5 to run a couple of wires behind the dash for an
aftermarket brake control. All the popular controllers can be ordered
with a Ford,
GM, Chrysler or Toyota plug -- wiring the RR with a
Ford plug would make the most sense. Meanwhile, we have to wire
up the new Range Rover manually for a
trailer brake controller, and the description below covers my own
installation.
Choice of Controller
There are two main types of trailer brake controller. The
least expensive are timer-activated, with braking effort increasing the
longer you have the brakes on. More expensive but much better are the
proportional inertia-activated units which sense the vehicle's
deceleration and aply the trailer brakes in proportion to it. Some
of
these are pendulum-operated and require calibration according to the
angle at which they are mouted, but the more expensive ones have
solid state inertial sensors and require no
calibration. I have had experience towing heavy braked trailers with
five different previous tow vehicles and brake controllers, and can
confirm from bitter experience that it is not worth economomising on
this item. In my experience, the cheaper, more crude controllers are
epecially annoying at very low speed when coming to a stop, or in stop
and go traffic -- in order to get sufficient braking effort at high
speed they have to be set so they jerk you around a lot at low speed.
Like most things in life, you get what you pay for.(we
are only talking about a $60-80 difference here anyhow).
I settled on the Tekonsha Prodigy, one of the more
expensive and widely used units at the time of writing, but any of the
more expensive controllers should do a good job. I
ordered mine with the generic wiring harness that includes a plug to
connect to the back of the device.
Positioning and Mounting the Brake Control
The
controller needs to be positioned where it can be reached while
driving,
both for adjustment and for emergency trailer brake application. I
decided to mount mine just above the storage pocket in the lower left
of the dash. The only problem with this is that the OBD-II/diagnostic
connector is located in the top of this pocket, so I had to be careful
to allow continued access to it. The resulting positioning is shown in
the photo a the top of the page.
Wiring
Connections Needed
All trailer brake controllers use 4-wire connections as follows:
+12 Volts (black)
Ground (white)
Brake switch input line (to tell the controller when you are aplying
the brakes) (red)
Output line to the 7-pin trailer plug (blue)
Access
Behind
the Dash
Some wires need to go through the firewall, and another along the
inside of the firewall to the right hand footwell. This requires
getting access to the area behind the dash. For more details on this,
see the dash
trim removal page that will be coming soon.
Probably the only panel you really need to get behind is the underdash
closing panel -- the flat horizontal one above the brake and
accelerator. However, getting it out entails first removing the
vertical center console closing panel (beside the accelerator on LHD
vehicles). Simply remove the one screw visible in this panel and then
pull it off downwards, outwards and rearwards to disengage its
remaining securing clips. Then you only have about 3 screws to remove
to take out the underdash closing panel.You can now see a convenient
gap above the front of the transmission tunnel where you can easily
pass the brake switch sense line through to the right hand footwell.
To run the necessary brake control output line back to the rear of the
vehicle, you will also need to remove the carpet trim panel along the
door sill, and the footrest and surrounding trim at the foot of the "A"
pillar. This in turn makes it easy to remove the left lower dash
finisher panel in which the little cubby pocket is mounted, giving
better access behind the dash and making it easier to make provision
for running the brake control plug wires out through the back of the
pocket itself. However getting this last piece off requires first
taking out the flat plastic fasia end panel, very easy to do by just
temporarily yanking the rubber door surround seal out of the way and
popping the panel out with a screwdriver.
All these panel removal operations will be depicted in more detail in
the dash panel removal page.
Photo: Lower left
dash area with trim panels removed for access as described above.
Dangling wires and plug are for trailer brake control.
Power Supply and Ground Lines
The +12 volt supply wire should be
connected as directly to the battery as possible, via a 20-amp self
resetting circuit breaker. (If you connect it to some vehicle circuit
controlled by one of the interior fuse boxes, there is a risk of losing
the trailer braking function when that circuit malfunctions or blows a
fuse). Accordingly, it is desirable to run the power supply and ground
lines through the firewall to access the battery. Fortunately, on
the RR III one of the major wiring harnesses goes through the firewall
just above above and to the left of the brake pedal. The harness is
enclosed in a rubber boot where it goes through the firewall -- so I
was able to expand it slightly to accmodate the additional wires (see
photos below).
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View from lower left footwell
with cover panels removed, showing the vehicle wiring harness going
through the firewall. The connector and wires for the trailer brake
controller are also visible.
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Close-up of harness passing
through firewall, via a flexible rubber boot.
Note trailer brake wires entering the rubber boot.
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Above: View from inside
engine
compartment, showing wiring harness (arrow) passing through firewall
beside brake servo and fluid reservoir. Harness is surrounded by a
flexible rubber boot. Black and white twisted pair of wires is from
trailer brake control.
Above Right:
Closeup of wiring harness
exiting boot attached to firewall. Insulation is peeled away from the
wiring harness next to the rubber boot. Arrow points to hard plastic
sheath around wiring harness; trailer brake wiring is passed between
this and the rubber boot.
Right:
Insulation sealed up again with electrical tape
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Note that as shown in the photos above, I removed the black
electrical tape that sealed the harness to the rubber boot. Under the
tape there is a gooey black insulating substance around the harness
wires; I also unnecessarily removed some of this in order to see if I
could feed the brake controller wire through with the other wires. In
the event, this looked nearly impossible, and might also damage the
other wires. So I decided instead to feed them outside the hard plastic
sheath around the harness wires, but inside the much more flexible
rubber boot. This avids the possibility of damaging the other wires.
From inside the car, I found it easy to "feel" where the hard sheath
was and feed the wires through outside it. To get them through the last
inch or so, I pried the rubber sheath up with a pair of pliers to
create a gap to push the wires into through. Then I protected
them with spiral wrap and fed them under the HEVAC intake vents across
to the other side of the engine to the battery compartment see photos
below).
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Above: +12V & ground
wires (enclosed in black spiral wrap) threaded under HEVAC intake
vents to battery compartment.
Top Right:
Battery compartment looking from above -- positive terminal at top
of photo. Thick red cable supplies jump start terminal. Black spiral
wrap encloses brake control +12 and ground wires. White wire grounded
to chassis with sheetmetal screw in existing hole. Black wire connected
to circuit breaker also mounted to chassis. Circuit breaker input is
thin red wire from +12 jump start terminal. After connection,
insulation (not shown) should be applied to circuit breaker.
Right: +12 volt
connection (thin red wire) is threaded from battery compartment through
existing hole to jump start terminal. Plastic cover (shown open)
encloses connection when closed.
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The jump start terminal makes a very convenient connection point for
the +12 wire. From this terminal, the wire should go through a 20 amp
self-resetting circuit breaker (available at any auto parts store)
before the connection to the brake control. I mounted the breaker near
the battery and ran the supply wire to it from the jump start terminal
through an existing hole in the front wall of the battery compartment
(see photos above). Make sure you get a good ground for the white
battery control wire; the instruction manual
warns against
using steel parts of the under-dash structure which might not be well
grounded to the chassis. I grounded it to the chassis using
a self-tapping screw in an existing small hole next to the battery
(photo above).
Brake Switch Sense Line
On most vehicles this can simply be connected to the mechanical switch
behind the brake pedal that activates the brake lights. However the
Range Rover LM, like its relative the BMW X5, uses a solid state
Hall-effect sensor for this function, and connecting anything to it is
not recommended. (The BMW X5 site has some interesting discussion on
this topic). The sensor's status is detected by the Light Check Module
(LCM) which controls all the vehicle's lights, so the best thing to
connect to is the LCM output that tells the trailer ECU that the brake
lights are on. (Do not select one of the other outputs that
controls the actual brake lights, because these can carry bulb test
signals even when the brakes are not on). You can intercept this
"brake status" wire either at the LCM itself, which is located behind
the "A" pillar trim in the right hand footwell, or at the rear fusebox
where it enters the trailer ECU. This Blue/Black wire comes from pin 10
on the LCM connector C0937, (which is the one at the top of the LCM),
and runs via the wiring harness to the rear of the vehicle. My RAVE
manual does not give
pinouts for the trailer ECU, but you can find the same color wire there
and connect to it.
I decided to connect my brake switch sense line to the LCM, which was a
shorter run of wire
and meant I would only have to run one wire (the controller output
line, see below) all the way back to the rear of the vehcle. Once you
have removed the panels under the dash (see dash trim panel removal
page), it is a simple matter to run
the wire across to the right hand side of the vehicle behind the
glovebox, and connect it to the appropriate LCM output wire (see photos
below).
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Red brake switch sense wire
threaded through gap above transmission tunnel to reach the Light Check
Module mounted on the RH footwell "A" pillar. Top photo is view from
left footwell; lower photo is view from right footwell, both with trim
panels removed.
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Red brake switch sense wire
connected to Black/Blue wire coming out of top connector of the Light
Check Module (LCM) -- the black box in this picture, mounted to the
lower right "A" pillar. Corner of glove box is at extreme top right of
photo
(LHD vehicle).
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Illustration of access to LCM
harness without removing the right lower dash finisher and fascia end
finisher. You can just dig the Blue/Black wire out of this bundle and
connect to it.
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The LCM is mounted against the lower "A" pillar in the RH
footwell. I found it convenient to dismount it from the pillar
and remove the connector to facilitate access to the wires, but you
don't really need to do this. The right hand photo above with the right
hand lower dash finisher still in place shows how you could perform
this connection without even removing that item (which also requires
removing the fascia end finisher). In either case, you can use the blue
jumper connector supplied with the brake controller harness to make the
actual connection.
Controller Output Line
Running the (blue) brake controller output line back to the rear of the
vehicle to connect with
the unused wire on the official trailer harness means somehow getting
from the left front to the right rear of the vehicle's interior. After
some thought I decided to run this wire behind the dash alongside the
brake switch sense wire to get to the right hand side of the car, then
run it straight back under the sill plates and "A", "B" and "D" pillar
trim panels. I had already removed most of these once before to clean
up a milk spill in the rear passenger compartment, so I knew it wasn't
too tricky. (More details on removing and replacing these trim panels
see the separate page on this topic, coming soon). The
following photos and description depict the routing I used.
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Photo taken from right front
footwell looking forward. Blue brake control wire is routed across from
top left behind lower dash closing panel, then down lower "A" pillar to
the door sill.
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Right front door sill plate
removed to allow routing of wire under it towards rear of vehicle.
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The lower "A" pillar trim panel and front
right sill plate were already
removed anyhow for the previous step (connecting the brake switch sense
line to the LCM -- see above). The next step is to remove the right
rear sill plate (it simply pops up under the influence of leverage from
a screwdriver), allowing you to pull the lower "B" pillar trim off.
This also just pops out when you pry it with a screwdriver. There is no
need to remove it entirely -- just pull the lower half of it out from
the pillar toward the vehicle interior) to allow enough access to run
the blue wire behind it (see photo below left).
**NOTE: The shop
manual warns that your
should make the SRS system safe before removing this "B" pillar panel.
To
do this, remove the ignition key and disconnect the batttery for at
leat 10 minutes. The first time I removed the bottom of the panel I
neglected this step, but since I was not removing the top part where
the airbag is, I didn't seem to set off any explosions. However, as
always, follow my shortcuts at your own risk!!
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View from right rear passenger
footwell showing routing of blue brake control wire from front door
sill (top left of photo), behind the "B" pillar trim, under the lower
black plastic footwell trim, and along rear door sill (lower right of
photo).
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Rear footwell and door sill
showing routing of blue wire back along sill up the rear wheel arch.
Note lower "D" post finisher on inner wheel arch is removed -- see next
photos.
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This gets us back to the rear seat, and we only need to get
the wire
behind the lower "D" post finisher to reach the rear fusebox, which is
already uncovered from installing the factory trailer harness (above).
First, pull off the upper trim finisher by pulling it out from the top.
(This is easier if you pull off the adjacent section of rubber door
seal). With this panel removed you can access and remove the two Torx
screws that hold the top of the lower panel in place. Then, simply lift
the lower trim panel up to release the pegs at its lower edge, so the
entire panel can be removed. You should now have a clear shot for the
blue brake controller wire's connection to the unused blue wire
dangling from the recently installed trailer harness.
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Above Left: removing upper
D pillar trim finisher by pulling it out at the top.
Above Center:
This exposes the Torx screws holdin the top of the lower trim finisher.
Undo, pull top out and lift finisher up to remove.
Above Right:
With lower "D: pillar trim removed, brake control output wire can be
routed up the wheel arch and behind the loadspace trim (no need to
remove it -- you can see behind it) to the rear fusebox.
Right: Blue wire
continues back to connection with "unused" blue wire on trailer wiring
harness. I used a standard automotive wiring connector (see arrow).
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Reassembly
Tips
You can now reattach all the trim panels you have partially or
completely removed. As the manual so often says, reassembly is the
reverse of removal. However there are a few things to watch out for. In
most cases you can visually line up the various pegs and clips that
hold each trim panel on before you give it the final push. In the case
of the aluminum sill plates (called carpet retainers in the shop
manual), there are two kinds of fixings that need to be lined up. The
white plastic pegs on the outer edge of the plate slide freely along
the length of the aluminum extrusion from which it is made, so first
put the outer edge of the panel in place and line up these pegs with
the corresponding holes in the floor. Then when you
carefully lower the inner edge of the panel towards the floor, you can
see if the longitudinal blades line up with the clips in the floor. If
not, the floor clips can be slid left and right by hand until they do.
When everything liines up you can push down on the sill plate to
press it home. For more details see the upcoming trim panel removal
page.
Parts Sources
Factory Trailer Wiring Kit:
Atlantic
British -- has low prices on two versions of the kit with and
without the 4-pin adapter
The
Rover Connection -- low prices on all genuine parts including the
towing kit
Brake Controllers:
After shopping around, I got my Tekonsha Prodigy brake
controller at Camping World,
where the non-member price is $155 and the "Presidents Club" price is
$139. Subsequently, I found it was available less expensively through
Amazon.com! Relevant Amazon.com
links and some other sources I found for other brands of controller are
listed below.
Amazon.com
Tekonsha Search Results
-- Direct link to Tekonsha products
on Amazon.com (Tekonsha Prodigy was $119 last time I looked)
Amazon.com
Trailer Brake Controller Search Results -- A wide variety of controllers at
low cost.
NorthernTool.com
also have a variety of brake controllers and
replacement parts for trailer brakes.
JCWhitney.com
have several brake controllers and various other
towing accessories.
Partsamerica.com
have brake controls and other towing accessories
AutoAnything.com
have several controllers including the Tekonsha
Prodigy
More Information
Setting up a RR III for Towing
Trailer Wiring Harness Installation Page (RR III)
Dash
Trim Panel Removal Page (RR III/L322/LM) (Coming Soon)
BMW
X5 trailer brake controller installation (quite similar to RR
III) -- on "X5 World" website
Another
BMW X5 installation (also on the "X5 World" website).