Cummins
Automatic Transfer Switch / Output Contactor Failure
Generator runs but does not transfer power to the building
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Faulty automatic transfer switch (ATS) control board, Stuck or welded ATS contacts, Open generator main breaker, Incorrect control wiring between Cummins controller and ATS
How to Fix / Troubleshooting
Safety first: Working on transfer switches involves lethal voltages. Only qualified electricians should open ATS enclosures. Disable automatic start and lock out both utility and generator sources before inspection.
- Check generator output: With a meter at the generator terminals, verify correct voltage and frequency while running.
- Main breaker: Ensure the generator main breaker inside the enclosure is in the ON position and not tripped.
- ATS status: Observe ATS indicators. If it shows a fault or remains in utility position despite loss of utility, the ATS control or mechanism may be faulty.
- Control wiring: Verify the start/transfer control wires between the Cummins controller and ATS are intact and correctly landed per the wiring diagram.
- Service: If the ATS mechanism is stuck or the control board is faulty, arrange for ATS repair or replacement by a licensed electrician or Cummins dealer.
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Repair Difficulty
Professional Required
5/5
Required Part
Automatic Transfer Switch (ATS)
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