How do I fix a Mollom VFD that will not start after installation?
Answer
Recheck power wiring, motor connections, and the Run/Start command source before assuming the drive is defective. Confirm the VFD powers on, shows a ready state, and is receiving a valid start signal from the keypad, terminals, or control source set in parameters.
Before you start: stop right away if…
- VFDs use dangerous mains voltage. Isolate power and use proper lockout before inspecting terminals.
- Incorrect motor or parameter settings can damage the motor or drive; change only values you understand from the manual.
Follow these steps
Verify the drive powers up safely
With covers in place, apply power and confirm the display or keypad lights. Note any fault code, ready status, or blank screen before pressing Run.
You should see: The VFD shows a normal powered state, or you have a specific fault code to look up.
Confirm supply and motor wiring
Power down and lock out, then verify line voltage wiring to the input terminals and motor wiring to the output terminals match the manual. Check that ground connections are secure and that any jumper or enable terminal required by the model is installed.
You should see: Input, output, and enable wiring match the installation diagram for that Mollom VFD.
Check the start command source
Power on again and confirm whether Start/Run is set to keypad, terminal, or communications. Send a start from the selected source only, and verify any external Run contact or switch is closed if terminals are used.
You should see: The drive receives a valid run command from the source configured in parameters.
Review basic motor parameters
Set motor voltage, frequency, and current to the motor nameplate values within the VFD’s allowed range. Correct an obviously wrong max frequency or control mode if the drive stays inhibited.
You should see: Motor parameters look consistent with the nameplate and the drive is no longer blocked by an inhibit or parameter error.
Use the manual fault list or support if it still will not run
If the VFD still will not start with correct wiring and a valid run command, record the exact status text or code and follow Mollom’s official troubleshooting for that model, or contact a qualified drive technician.
You should see: You have a model-specific next step, or a technician can diagnose hardware failure safely.
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Extra tips
What to look for: Whether the keypad powers on, any fault or status codes, and whether a Run/Forward command is actually being sent from the keypad or control terminals.
Before you change anything: Isolate power and follow lockout/tagout before touching mains or motor wiring. Photograph the current wiring and parameter settings before changes. Confirm supply voltage matches the VFD nameplate. If you are not trained with mains equipment, stop and use a qualified technician.