First identify what the contactor does when a START command is given. An open permissive, missing or low control voltage, incorrect coil rating, failed coil or mechanical obstruction may prevent pickup. The exact cause requires the approved starter drawing and competent inspection.
What the symptoms may mean
These observations help organize the investigation. They do not prove the root cause.
| Observation | Possible cause | Useful evidence |
|---|---|---|
| No sound or motion on START | Control supply, stop circuit, interlock or coil path | Control schematic and indicator status |
| Chattering or intermittent pickup | Low supply, poor control connection or contactor mechanism | Event history and control transformer records |
| Overload indication active | Protection or auxiliary-contact condition | Overload and fault history |
| Problem began after coil change | Wrong coil specification or wiring mismatch | Coil marking and replacement order |
Understanding the possible causes
DOL means direct-on-line
A DOL starter normally connects the motor to the supply through a contactor, with separate protection and control functions. The coil voltage may differ from the motor supply voltage. Use the installed drawing, not assumptions based on the motor nameplate.
Control permissions decide whether pickup is allowed
An emergency-stop circuit, STOP pushbutton, overload auxiliary contact or process interlock can intentionally prevent startup. A device refusing to pick up may be doing exactly what a protective control design requires. Never bridge or defeat an interlock to force starting.
A coil is not always the failed part
Some contactors chatter because supply dips when commanded. Others fail to seat because of mechanical wear or contamination. Replacing coils without understanding operating conditions can lead to recurring failures.
The correct response depends on the environment
A starter supplying a pump, compressor or critical process may have additional permissives from pressure, temperature or plant controls. These must be assessed by a qualified technician under site procedures before any intrusive testing.
Questions to narrow the problem
Collect existing operating records first. Inspection or electrical testing requires a qualified person and appropriate authorization.
- What motor and starter ratings appear on the nameplates?
- Is the contactor completely silent, humming or chattering?
- What do the overload, emergency-stop and local fault indicators show?
- Was wiring or a coil recently replaced?
- Is there an approved DOL circuit diagram or PLC interlock description?
What to do next
Preserve the existing fault indication and collect the starter schematic, coil specification and recent maintenance history. Have authorized staff review control permissions and contactor condition under electrical isolation procedures.
Common questions
Does a DOL contactor fault mean the motor has failed?
No. The starter control and protection circuit can prevent an otherwise healthy motor from starting.
Should the overload contact be bypassed to test the starter?
No. Defeating a safety or protection device can create an unsafe start condition.
Technical references
The linked sources explain general fault principles. The site-approved equipment manual and protection design take precedence.
- Schneider Electric: Model 6 MCC troubleshooting chart
- Schneider Electric: TeSys T motor management installation information
Record your electrical fault
Electrical Doctor helps organize symptoms and prepare preliminary case notes. It does not authorize repair or switching work.
Open Electrical Doctor Request an engineering assessment