Cummins/Onan — Power Relay Check (A11-K12)
Testing & diagnosis · Power relay A11-K12
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAQ, Cummins/Onan HDKAR
Procedure
- Unplug CB12-2A from the circuit breaker, noting wire markings to select the correct one.
- Locate S6 (oil pressure switch) and find the grounded side using a continuity tester.
- Use a jumper to ground the non-grounded side of S6.
- Use a second jumper from B+ on the control board to apply B+ to the SW B+ terminal; fuel pump E5 should start and run.
- Remove the B+ jumper. If the fuel pump continues to run, K12 is good; if it stops, replace the A11 control board.
- Push the generator set STOP button.
- Remove the jumpers and reconnect CB12-2A.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan HDKA →, Cummins/Onan HDKAQ →, Cummins/Onan HDKAR →
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.