JCB
ATS Control / Interlock Fault
Automatic transfer switch (ATS) does not transfer to generator supply during mains failure, but generator runs normally.
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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 ATS control coil, Broken control wiring between JCB controller and ATS, Incorrect ATS configuration, Mechanical interlock jammed
How to Fix / Troubleshooting
Safety: Work on ATS only when both mains and generator sources are isolated and locked out.
- Check ATS status: Observe indicator lights and mechanical position of the ATS. Confirm it is not stuck between positions.
- Control signal: Verify that the JCB controller is sending a transfer command (check output relay status).
- Coil voltage: Measure voltage at the ATS transfer coil when a transfer should occur. If absent, trace control wiring back to the generator panel.
- Mechanical inspection: Inspect ATS mechanism for dirt, corrosion, or mechanical damage preventing movement.
- Replace faulty parts: Replace defective coils or aux contacts and retest under simulated mains failure.
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Repair Difficulty
Hard
4/5
Required Part
Automatic Transfer Switch
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