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7-way Nose Box Tips:
• Inspect circuits inside the 7-way box for excessive electrical
resistance caused by overheating, corrosion, loose/poor
connections, or undersized wiring.
• Check to see if the 7-way nose box is equipped with circuit
breakers (see Figure 17), as the problem may be a failing
circuit breaker. Either replace circuit breaker with a new part
or connect the blue wire from the Select Controller to the
unprotected side of the circuit breaker. Circuit protection is
provided by the 30 amp fuse inside the Select Controller.
• Ensure the 7-way or stinger cord has a tight fit and has good
electrical contact at the tractor and trailer receptacles.
Figure 17: 7-Way Nose Box
SERVICE TIP - Purkeys offers the Liftgate Double Check
tool, which can simplify the diagnosis of liftgate charging
system problems caused by excessive voltage drop. For
more information on the tool, please call 1-800-219-1269 or
visit our website at www.purkeys.net.
Step 2: Disconnect the 7-way cord, apply a load of about 25
amps between the AUX and ground pins, and measure the
voltage. Voltage must remain above 10.5 volts. If not, test the
7-way cord and the wiring in the truck (wires from truck battery
to 7-way connection on truck).
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