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Freightliner install information
This is supplement
information for Freightliner chassis.
I purchased a wiring harness from Freightliner that
leads to cockpit exhaust brake switch. With the use of
continuity checker found the following:
The power supply wire is a White wire and is marked 119C EXH
BRAKE SUPPLY
The wire from ECM is a Red wire and is marked N15-C981 EGN RTRDR
Start at switch and follow the harness to a more covenant spot to
work on it. Just remove tape wrapped around harness to expose wires.
Attach BrakeSwitch wires to these wires.
BrakeSwitch has 6 wires:
2 Red 2 White 1 Purple 1 Black (The color is for identification
only)
Cut 119C EXH BRAKE SUPPLY wire, reconnect the
circuit by attaching each with a White wire leading to BrakeSwitch
control box.
Cut N15-C981 EGN RTRDR wire, reconnect the circuit by
attaching each with a Red wire leading to BrakeSwitch control box.
| There is a bundle of wires coming up the steering
column. It is the bundle going to turn signal. In this group is a
red wire with 36E on it. I am told this is a brake light
source and can be used to connect to the Purple wire. The black wire
goes to GND. |
Below is the additional Freightliner
information we have been sending with instructions.
Freightliner
Chassis Brake Source
If this does not work, in the cockpit on the forward
bulkhead (at base) there are two electronic boxes. The box on left
(street side) has the Brake Lamp relays. There is one wire in and
two wires out. In most cases the out wires are Red. (One small wire
and one heaver in size) When you apply brakes these wires are hot.
Connect to the larger of the two wires. The reason for this is: On
the Freightliner chassis there is a blocking diode in the brake
light circuit that blocks the return power to brake light switch. By
going to brake light relay you by-pass this diode. We use the brake
light circuit to turn on our relays by applying the brake pedal. The
exhaust brake turns on the brake lights and we use this to keep the
relays closed.
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