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Power Requirements for ABS
For trailers built after March 1 of 1998, the trailer wiring system must provide
two sources of power for the antilock system.
1. Full-time power (when ignition is on) must be provided by the tractor. This
full-time power source may be shared with other trailer circuits. The SAE
J560 Blue (AUX) circuit is commonly used as the full-time power source.
In other cases, a separate ISO 3731 connector is provided.
2. Brake light power. This input provides a source of backup power for cases
where an older tractor (without full-time power) is used to tow a trailer or
in case of a failure of the permanent power source.
Industry standards (TMC RP-137 and SAE2247) require that the tractor
provide at least 10 amps at 12 volts at the trailer end of the SAE J560 or ISO
cable on all ABS power circuits. Suppliers of Trailer ABS have agreed to
provide for proper antilock brake operation down to a minimum of 8.5 volts.
The ABS malfunction lamp will light if voltages drop too low to maintain reliable
solenoid operation.
Wabash National antilock systems operate at voltages down to 7.0 volts.
Current requirements are approximately 330 milliamps per control unit and
1.25 amps per PCM.
ABS Malfunction Lamp
Rules for the location, color, labeling, intensity and photometrics for external
ABS malfunction lamps have been established by the National Highway
Transportation Safety Administration (NHTSA). These requirements are
effective as of March 1, 1998.
Location
The lamp mounting location shall be near the left side rear of the trailer, no
closer than 150 mm (5.9 inches) and not more than 600 mm (23.6 inches)
from the rear red side marker indicator lamp. On a converter dolly, the lamp
mounting location shall be on a permanent structure of the dolly at least
375 mm (14 inches) above the road surface. After March 1st, 2001 a second
ABS malfunction lamp must be located in the cab.
MBS-1P Installation
7
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