PlantFlow 3D › Guides › Troubleshooting a motor control circuit step by step
Troubleshooting a motor control circuit step by step
A safe and logical method to find why a motor does not start or stops: symptoms, visual checks, the voltage trace, and dead testing.
Start with the symptom
Ask exactly what happens. Does nothing happen when START is pressed? Does the contactor pull in but the motor hums? Does the motor start and stop after some minutes? Each symptom points to a different part: control circuit, power circuit or protection.
Then look before you measure: a tripped breaker, an overload showing “tripped”, burnt marks, loose wires and indicator lamps tell you a lot in seconds.
The voltage trace (live testing)
If the contactor does not pull in, follow the control voltage from the supply to coil terminal A1, measuring against N. The voltage is lost at the first open element: a tripped overload (95-96), a pressed or faulty STOP button, a broken wire, or a START contact that does not close. If A1 has 230 V, measure across A1-A2: 230 V there with no pull-in means an open coil or a missing neutral on A2.
For a motor that hums but does not turn, measure the three phases at the contactor output and at the motor terminals: a missing phase gives single-phasing, which also trips the overload.
Dead testing and repair
When you have found the suspect part, isolate, lock off and prove dead. Confirm with continuity or resistance, replace or repair, then tighten terminals and check the wire numbers against the drawing.
Before handing back, test the circuit: START, STOP, the overload TEST button, the emergency stop and any interlocks. Write down what you found and changed.
Typical faults
Open or loose control wire, overload tripped by a lost phase, STOP button contact worn, contactor coil open, wrong coil voltage, seal-in contact 13-14 not wired (motor runs only while START is held), and a motor connected in star instead of delta.
Try it yourself
Open the 🔧 Troubleshoot tool on the Wiring tab. Pick the item that does not work and follow the voltage step by step until it is lost. The practical lessons hide real faults for you to find.
Open the PlantFlow 3D simulator →Safety: this guide explains principles for learning. Real installations must follow the applicable codes, the equipment manufacturer's instructions and the approval of a competent, qualified person. Isolate, lock off and prove dead before touching any circuit.