What causes fault code VFD-MCON1 (VFD Output Contactor Feedback Fault)?

Output contactor coil failed — not pulling in. Contactor auxiliary contact (aux block) failed or wiring disconnected. Control voltage to contactor coil missing — fuse blown or interlock open. Contactor contacts welded shut — aux feedback shows closed when main contacts are actually open (dangerous). Wiring error — aux contact wired NO instead of NC or vice versa

How do I fix fault code VFD-MCON1?

Check contactor — command it ON from PLC and verify physical pull-in (listen for click, check indicator). Verify aux contact status matches main contact state — when contactor pulls in, aux should change state. Check contactor coil voltage — measure at coil terminals when energized. If contactor pulls in but aux contact doesn't change, replace aux contact block. Verify wiring matches VFD manual — some require NO feedback, others NC. Check for welded contacts with contactor de-energized — main contacts should be open, verify with ohmmeter

VFD Output Contactor Feedback Fault

VFD-MCON1

VFD expected to see output contactor auxiliary contact feedback but did not. Drive will not run if contactor is not confirmed closed.

high vfd

vfd contactor feedback auxiliary interlock

Probable Causes (ranked)

Output contactor coil failed — not pulling in
Contactor auxiliary contact (aux block) failed or wiring disconnected
Control voltage to contactor coil missing — fuse blown or interlock open
Contactor contacts welded shut — aux feedback shows closed when main contacts are actually open (dangerous)
Wiring error — aux contact wired NO instead of NC or vice versa

Fix Steps

1 Check contactor — command it ON from PLC and verify physical pull-in (listen for click, check indicator)
2 Verify aux contact status matches main contact state — when contactor pulls in, aux should change state
3 Check contactor coil voltage — measure at coil terminals when energized
4 If contactor pulls in but aux contact doesn't change, replace aux contact block
5 Verify wiring matches VFD manual — some require NO feedback, others NC
6 Check for welded contacts with contactor de-energized — main contacts should be open, verify with ohmmeter

Field Trick

When output contactors start buzzing or chattering, replace them. That buzzing means the contacts are bouncing, which creates arc damage on every bounce. A chattering contactor will weld shut within a week. Don't wait for the failure.

Suggested Replacement Parts

Parts matched to fault category: Contactor

Allen-Bradley 100-C09D10 Contactor P/N: 100-C09D10 9A, 120VAC coil, 3-pole, 1 N.O. aux contact

AutomationDirect $45.00 Amazon $35.00 Grainger $65.00

Schneider LC1D09G7 Contactor P/N: LC1D09G7 9A, 120VAC coil, TeSys D, 3-pole

AutomationDirect $38.00 Amazon $30.00 McMaster-Carr $52.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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