Operating Instructions - Section 30 7/09 OM3050 Page 30-20 TOWING Special Wiring Harness Before towing, a special wiring harness must be made in order to release the parking brake. The harness will require approximately 9 meters (30 ft) of #14 wire, and one ON/OFF switch (capable of carrying 2 amps of current) and two ring terminals. Using a ring terminal, one end of the wire must connect to a 24VDC bus bar (1, Figure 30-2) in the auxiliary control cabinet to supply 24V to the solenoid. Switch (2) must be positioned in the harness so the operator can operate the switch while seated in the operators seat.
The harness must be fitted with a connector (4) to allow it to be plugged into parking brake solenoid (3) inside the brake cabinet. Wire (5) leading from this connector is to be connected to the ground block using a ring terminal. Refer to Figure 30-3 for an overview of the special wiring harness when installed on the truck. Before towing a truck, many factors must be carefully considered. Serious personal injury and/or significant property damage may result if important safety practices, procedures and preparation for moving heavy equipment are not observed. A disabled machine may be towed after the following precautions have been taken. Do not tow the truck any faster than 8 kph (5 mph).
Tow with a solid tow bar. DO NOT tow with a cable. Use a towing device with ample strength for the weight of this truck. The parts required to connect to the solenoid are: 1 housing (PB8538), 2 sockets (0819105430) and 1 wedge (PB8540). Never tow a truck on a slope. Inspect towing components, such as tow bars and couplings, for any signs of damage. Never use damaged or worn components to tow a disabled vehicle. Towing Procedure 1. Shut the engine off. Keep a safe distance from the trucks and towing apparatus while towing a vehicle. 2. Block the wheels on the disabled truck to prevent movement while preparing the truck for towing and while attaching the tow bar.
After connecting a truck that is to be towed, do not allow anyone to go between the tow vehicle and the disabled vehicle. 3. Ensure the towing vehicle has adequate capacity to both move and stop the towed truck under all conditions. Set the coupling of the truck being towed in a straight line with the towing portion of the tow truck, and secure it in position. 4. Ensure that the tow bar has adequate strength (approximately 1.5 times the empty vehicle weight of truck being towed). Install tow bar between the two vehicles. An operator is to remain in the cab of the towed vehicle at all times during the towing procedure. 5.
Block the wheels on the tow vehicle to prevent movement while preparing the disabled truck for towing. 6. If necessary, install quick disconnect fittings to the bleeddown manifold to allow the hydraulic system to be operational. Install hydraulic connections for steering/braking between the tow vehicle the and disabled vehicle. An auxiliary power unit can also be used. For additional information on hydraulic connections, refer to Disabled Truck Operation, this section. 7. After the hydraulic connections are made, check the disabled vehicle braking and steering systems for normal operation.
Install 24 100 kPa (3,500 psi) pressure gauges on both the BF test port and the BR test port on the brake manifold in the brake cabinet. Ensure proper pressure is displayed on the gauge when depressing the brake pedal. 1. 24VDC Connection 2. Switch (ON/OFF) 3. Park Brake Solenoid FIGURE 30-2. PARKING BRAKE HARNESS 4. Connector 5. Ground Wire