Usage:
784B (5RK) Tractor, 785 (8GB),
785B (6HK),
789 (9ZC),
789B (7EK),
793 (3SJ),
793B (1HL),
793C (4AR) Off-Highway Trucks
Description of Change: For some off-highway trucks equipped with both Automatic Retarder Control (ARC) and dual brake relay valves, the dash panel light that was previously referred to as the "Retarder" light will now function as a Brake Light. For all off-highway trucks equipped as described above, the Brake Light will illuminate when the Automatic Retarder Control (ARC), Retarder, and/or Service Brakes are applied.
Adaptable To: This change is effective with all 784B (5RK22-Up) Tractors, 785B (6HK602-Up), 789B (7EK455-Up), 793B (1HL463-Up), and 793C (4AR79-Up) Off-Highway Trucks. Listed below are model serial numbers for all trucks as equipped by the manufacturer which may be affected by the change described above. The ONLY trucks affected are those presently operating with both Automatic Retarder Control (ARC) and dual brake relay valves installed.
The following model serial numbers include trucks which may or may not have been equipped with Automatic Retarder Control (ARC) and which were NOT equipped with dual brake relay valves by the manufacturer: 785 (8GB1-697), 785B (6HK1-432), 789 (9ZC1-677), 789B (7EK1-277), 793 (3SJ1-56), and 793B (1HL1-194) Off-Highway Trucks.
The following model serial numbers include trucks which have been equipped with Automatic Retarder Control (ARC) and which were NOT equipped with dual brake relay valves by the manufacturer: 784B (5RK1-21) Tractors, 785B (6HK433-601), 789B (7EK278-454), 793B (1HL195-462), and 793C (4AR77-78) Off-Highway Trucks.
NOTE: Service Magazine Supplement articles for off-highway trucks listed above will also follow to update Operation and Maintenance Manuals with corrected operation information for Brake Lamps.