From Table 2A, what is the probable cause if the symptom is 'Failure of equipment to start with contactor closed'?

From Table 2A, what is the probable cause if the symptom is 'Failure of equipment to start with contactor closed'?

• A. Coil shorted
• B. One contact not closing
• C. Power supply failed
• D. Overload tripped

Answer: (B)

When the equipment won’t start even though the contactor appears to be closed, the most likely issue is that one of the main contacts isn’t closing. The coil may energize and pull the contactor in, but if a single contact in the power path remains open, the circuit isn’t complete and the motor won’t receive power. This can happen from wear, pitting, or binding that prevents one leg of the circuit from making contact, even though the other contacts have closed properly. If the coil were faulty (for example, a coil short), the contactor might not close at all or could behave unpredictably, not simply leave one contact open. A power supply fault would prevent the coil from energizing, so the contactor wouldn’t close in the first place. An overload protection event typically trips or interrupts the motor circuit rather than leaving the contactor with one contact stubbornly not closing, so it wouldn’t directly explain “equipment won’t start with the contactor closed.”

When the equipment won’t start even though the contactor appears to be closed, the most likely issue is that one of the main contacts isn’t closing. The coil may energize and pull the contactor in, but if a single contact in the power path remains open, the circuit isn’t complete and the motor won’t receive power. This can happen from wear, pitting, or binding that prevents one leg of the circuit from making contact, even though the other contacts have closed properly.

If the coil were faulty (for example, a coil short), the contactor might not close at all or could behave unpredictably, not simply leave one contact open. A power supply fault would prevent the coil from energizing, so the contactor wouldn’t close in the first place. An overload protection event typically trips or interrupts the motor circuit rather than leaving the contactor with one contact stubbornly not closing, so it wouldn’t directly explain “equipment won’t start with the contactor closed.”