Usage:
Challenger 65C (2ZJ1-546),
Challenger 70C (2YL1-238),
Challenger 75C (4KK1-558),
Challenger 85C (9TK1-365) Agricultural Tractors
Reference: Special Instruction, SEHS7633, Battery Test Procedure
The 9X-0253 Switch (Main Power Relay) may not work properly on the machines above. The 5/16-24 full nuts that secure the power terminals on the main power relay may not be tightened to the proper torque. A complaint that some electrical circuits work intermittently or not at all may be experienced. The circuits controlled by the relay include: heater & A/C blower, A/C clutch, 3 point hitch, front/rear wipers, horn, and front/rear flood lights.
This problem is most likely to occur with Challenger 65C (2ZJ1-546), Challenger 70C (2YL1-238), Challenger 75C (4KK1-558), and Challenger 85C (9TK1-365) Agricultural Tractors.
With the engine off, troubleshoot to verify an intermittent or open circuit at the main power relay. Use a 6V-7070 Multimeter (or equivalent) set on DC voltage to determine if the main power relay (located on right front frame next to engine) has a complete circuit from the key switch to energize the coil of the relay. The coil terminals of the relay are the small 10-32 thread studs and there should be a 123-White wire on one stud and a 200-Black wire on the other stud. With the keyswitch in the "on" position, there should be system voltage on the coil terminals. If the system voltage is not on the coil terminals with the keyswitch in the "on" position, further troubleshooting must be done to find the "open" in the coil circuit. Refer to the electrical schematic for the circuit path to the relay coil and troubleshoot for the open circuit.
If system voltage is on the coil, check the voltage on the relay power terminals (contacts). These are the large 5/16-24 studs. A 112-Purple wire will be on one stud and a 109-Orange wire will be on the other stud. With the relay energized (system voltage on coil terminals), measure the voltage from a good ground on the machine frame to the stud with the 109-Orange wire, note this reading. Then measure the voltage from the same ground to the 112-Purple wire. The voltage at the 109-Orange wire minus the voltage at the 112-Purple wire should be .5 volts or less, this is the contact voltage drop across the relay contacts. If the contact voltage drop is greater than .5 volts, the relay should be replace OR the connection tightened. If system voltage is not present at the 109-Orange wire, refer to the electrical schematic for the circuit path and troubleshoot for the open circuit.
If the terminals for the 112-Purple or 109-Orange wires are loose on the studs, the relay may have been damaged. If either stud is discolored or has a dark appearance, the stud has probably been hot from a loose connection and the relay must be replaced. If the studs appear normal, then the connection just needs to be tightened. Loosen the full nut holding the terminals in place and tighten the half nut below the terminal to 6 ± .5 N·m (4.4 ± .37 lb ft). (If the threads appear to be damaged, too much torque may have been used at assembly and the complete relay should be replaced.) Next, while holding the large terminal in place, tighten the full nut to 6 ± .5 N·m (4.4 ± .37 lb ft). If replacement hardware is needed the half nut is a 4F-2294 Nut and the full nut is a 6V-8186 Nut. Be sure not to over-tighten the connection as the 5/16-24 power stud is copper and the threads will be damaged if too much torque is applied. For reference purposes, the smaller studs for the coils wires are 10-32 threads and the replacement nut for it is a 6V-8378 Nut. These nuts should be tightened to a torque of 2 ± .25 N·m (1.48 ± .185 lb ft).
NOTE: Be sure to disconnect the negative (-) battery cable at the frame ground stud in the battery box BEFORE replacing the relay or tightening connections while troubleshooting. Also, system voltage can vary widely depending on state of charge of the batteries, anywhere from 12.0 to 12.75 Volts DC with the engine off. Reference Special Instruction, SEHS7633, Battery Test Procedure for more information on batteries.
The correct tightening torque is being used, effective with Challenger 65C (2ZJ547), Challenger 70C (2YL239), Challenger 75C (4KK559), and Challenger 85C (9TK366) Agricultural Tractors.