Why does the contactor click but the motor won't start?

A contactor that pulls in proves the control circuit and the coil are working. The fault is downstream: a blown power fuse, burnt or pitted main contacts that close but don't conduct, an open overload or disconnect in the power path, a damaged motor lead, an open motor winding, or a seized load. Measuring voltage on the load side of the contactor tells you which half of that list you're in.

What does it mean if the motor hums but doesn't turn?

A three-phase motor that hums but won't turn is usually single-phasing (one of the three phases is missing, from a blown fuse, a burnt contactor pole, or a loose lug) or it's trying to start a seized load. Don't keep re-trying the start: a stalled or single-phased motor draws locked-rotor current and heats up fast.

Can the control circuit be fine while the power fuses are blown?

Yes. On many starters the control circuit has its own fuses or its own control transformer, so the contactor coil still pulls in even when one or more main power fuses are open. That's exactly why the click alone doesn't prove the motor is getting power.

Troubleshooting guide

Motor Won't Start but the Contactor Clicks? Find the Break in Order

You hit start, you hear the contactor pull in — and the motor does nothing. Or it just hums. That click is good news: it just eliminated half the circuit for you. Here's how to find the break in the other half without swapping parts.

Last updated: October 2026 · written and reviewed by a working maintenance professional

This one gets a lot of people because the contactor sounds like it's working. It is working — partly. And that's the clue most people walk right past.

When a contactor pulls in, it proves the whole control side did its job: the start button, the stops, the interlocks, the coil, control power — all fine. Every one of those can come off your list. What the click does not prove is that power is actually reaching the motor, or that the motor can turn. So the fault lives in one of two places: the power path from the line to the motor, or the motor and its load.

One safety note before the steps: the voltage checks below are live work on the power side. Only do them if you're qualified, with the right PPE for the panel, and lock out before you touch a conductor or anything that turns.

Step 1: Listen — hum or silence?

It's free, it takes five seconds, and it splits the problem in two.

Dead silent when the contactor pulls in: the motor is getting no power at all, or nowhere near enough. Think open circuit — fuses, contacts, an open disconnect, a broken lead.
A hum or growl, but no rotation: the motor is getting some power. On a three-phase motor that almost always means one phase is missing (single-phasing) or the load is locked up. Don't keep hitting start. A stalled motor draws locked-rotor current and cooks itself fast — give it one try, then diagnose.

Step 2: Line side of the contactor — is power arriving?

Measure phase-to-phase on the line terminals (L1–L2, L2–L3, L1–L3). All three should match within a few percent. If one reading is low or zero, the problem is upstream: a blown power fuse, a tripped breaker, an open disconnect, a loose lug feeding the starter.

Here's the trap: on a lot of starters the control circuit has its own fuses or its own control transformer. So the coil happily pulls in even when a main power fuse is blown. The click convinced someone the power was fine. It wasn't.

Step 3: Load side, with the contactor pulled in

Now command the start and measure the load terminals (T1–T2, T2–T3, T1–T3) while the contactor is held in.

Line side good, load side missing a phase: the contactor's main contacts are closing but not conducting. Burnt, pitted, or welded-open poles do this. The coil works, the armature moves, and one pole carries nothing. That's your hum.
Load side good on all three: the contactor isn't your problem. Keep following the power toward the motor.

Step 4: Follow the power to the motor terminals

Between the contactor and the motor there are usually a few more places for a phase to disappear: the overload relay's heaters or current path, a local disconnect at the motor, a junction box, and the cable itself. Measure at each point until the voltage drops out. Wherever it goes missing is where the break is.

If you've got full, balanced voltage right at the motor terminals and it still won't turn, the power path is innocent. The fault is the motor or what it's driving.

Step 5: Lock out — then test the motor and turn the load

With everything locked out and verified dead:

Turn the shaft by hand (or the driven equipment, if it's coupled). A seized bearing, a jammed conveyor, or a pump packed solid will stall the motor every time. The electrical side is fine; the load isn't.
Check winding resistance phase to phase. The three readings should be close to each other. One open or way-off reading means a damaged winding or a bad connection in the motor box.
Megger the motor to ground (with the motor disconnected from the starter). A winding that's broken down to the frame can trip things the instant power is applied.

Reading about it is one thing. Doing it with the line down is another.

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The order is the whole trick

The click told you the control side is fine, so don't spend time there. Listen first, because it's free. Then measure line side, load side, and motor terminals, in that order, so you find the break instead of guessing. Lock out and turn the load before you condemn the motor. That's five checks, cheapest and fastest first, and it beats ordering a new contactor because "it's probably the starter."

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