Cummins/Onan — Bypass Switch Test

Testing & diagnosis · Bypass switch and interlock system

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

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Procedure

1. Same Source Bypass Test: turn and hold the Source Select switch to the normal source and move the bypass switch handle to the normal source position.
2. Turn the key operated Drawout Release switch, then turn the drawout crank handle counterclockwise until the amber test light comes on; release the Drawout Release switch.
3. If operational, no power interruption should occur; green Bypass Switch-Position and Transfer-Switch-Position lights should be ON.
4. Turn the Drawout Release switch and turn the drawout crank handle clockwise to the limit of rotation.
5. Release the Drawout Release switch and push the Reset switch; green Transfer-Switch-Position light should be ON.
6. Move bypass switch handle to the automatic position.
7. Dead Source Bypass Test: with generator set off, hold Source Select switch to emergency power side and attempt to move bypass switch handle to the emergency side; interlock should prevent transfer to
8. Opposite Source Bypass Test: with bypass switch in AUTOMATIC, move engine start switch to RUN; generator set should start and red Emergency Source light should come on.
9. Turn and hold the Source Select switch to the emergency source and move the bypass switch handle to the emergency source position.
10. Verify that the red Bypass-Switch-Position light is ON.
11. Move bypass switch handle to the AUTOMATIC position.
12. Allow generator set to run for 5 minutes and then turn engine start switch to STOP.

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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