Cummins/Onan — Block and Cross-Bar Assembly Removal and Replacement (40 to 125 Amperes)

Repair & overhaul

From a Cummins/Onan service manual — check it applies to your exact model before use.

Applies to: Cummins/Onan OTPC

Procedure

1. Remove the linear actuator as described for 40-125 ampere switches (steps 1-6 of Removing Actuator).
2. Remove the interlock bar from the interlock arms.
3. Disconnect the control wiring leads from the jumper bus bars.
4. Remove the hardware securing the jumper bus bars to the load bus bars and lift off the jumper bus bars.
5. Remove the control wiring leads from the power source terminals and remove the power source supply wires from the lug terminals.
6. Remove the two round head machine screws, lock washers, and flat washers securing the block assembly to the base; remove the assembly.
7. Clean all current-carrying surfaces with a wire brush.
8. Hold the block assembly in position and check alignment of the auxiliary switch lever; it must be aligned vertically when contacts are closed.
9. Secure the block assembly to the base with round head machine screws (2), lock washers (2), and flat washers (2); tighten to 25-30 in-lbs (2.8-3.4 Nm).
10. Install power source supply wires, control wiring to power source terminals, and the jumper bus bars with electrical joint compound; tighten as specified.
11. Apply thread sealant (Loctite 242, P/N 518-0309) to the interlock bar machine screws; install and tighten to 15-20 in-lbs (1.7-2.3 Nm).
12. Attempt to close both sides of the transfer switch; the interlock assembly must hold one side open.
13. Replace the linear actuator per steps 2 through 8 of Replacing Actuator; apply lubricant (P/N 524-0157) to the slot in the handle.
14. Test the switch for proper operation and close the cabinet.

Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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