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Home›Repair guides›Cummins/Onan›Changing Control Accessory Panel DC System Voltage (12 to 24 Volts)

Cummins/Onan — Changing Control Accessory Panel DC System Voltage (12 to 24 Volts)

Adjustments · Control accessory panel DC modules

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

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Before you start

  • Failure to remove AC power from the automatic transfer switch and to disable the generator set presents a serious shock hazard during this modification.

Procedure

  1. Open the automatic transfer switch cabinet door.
  2. Move operation selector switch to STOP.
  3. Disconnect the starting batteries.
  4. Remove AC line voltage from the automatic transfer switch.
  5. Remove the twist-lock disconnect plug and open the control accessory panel.
  6. Remove the wire lead from transformer T1 terminal T1-X2 and connect to terminal T1-X3.
  7. Remove the wire lead from resistor R1 terminal R1-2 and connect to terminal R1-3.
  8. Remove the 12-volt battery charger module 6 (300-0793) and replace with the 24-volt module 300-0794.
  9. Remove the 12-volt module 5 (300-0847) and replace with the 24- to 12-volt converter module 300-0848.
  10. Spec A and B only: remove the 12-volt start-stop time delay module 7 (300-0921) and replace with the 24-volt time delay module 300-0922.
  11. If module 9 is a 2 to 3 wire converter (300-0926), remove and replace with a blank (spare) 300-0937 module.
  12. If module 10 is a 12-volt battery voltage sensor (300-0796), remove and replace with a 24-volt sensor module 300-0797.
  13. 400 ampere AT only: remove the one screw from inside center support for left cabinet door and open door.
  14. Remove LO BAT VOLT lamp DS13 and HI BAT VOLT lamp DS14 and replace with 322-0126 and 322-0127 lamps respectively.
  15. Close panels, reconnect disconnect plug, connect a 24-volt battery, restore AC line voltage, move selector switch, close cabinet door.

Tools required

Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.

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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