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These 10 free C-204 questions are organized by exam domain, so you can see how each part of the Motor Control Troubleshooting 1 (C-204) blueprint is tested. Reveal the answer and explanation under each question.
During a permitted energized test, a fully pulled-in motor contactor carries approximately 18 A through each pole. Voltage measured directly across the line and load terminals of each pole is 0.08 V, 6.4 V, and 0.09 V. The terminal connections are secure, and coil voltage remains at its rated value. The second reading points to:
Correct answer: C - Excessive resistance inside the second contactor pole
After lockout, all links and external leads are removed from a six-lead motor. A digital multimeter (DMM) reads 1.80, 1.82, and 1.81 ohms across its three separate winding pairs. Each winding-to-frame measurement displays OL on the meter's 40-megohm resistance range. A coworker says this proves the insulation will withstand operating voltage. Which conclusion is justified?
Correct answer: D - The windings have continuity; insulation withstand at operating voltage remains unverified
Since a panel modification, a 50 VA, 24 V control transformer has run noticeably hotter during steady operation. Primary voltage and tap connections are correct. Its simultaneously energized loads are a contactor coil rated 60 VA pickup/10 VA sealed, a relay rated 8 VA sealed, pilot lamps totaling 6 VA, and a solenoid rated 40 VA sealed. Using the load ratings, what does the continuous-load check show?
Correct answer: D - 64 VA; the steady-state load exceeds the transformer's continuous rating
A technician clamps around all three phase conductors feeding a running pump and reads 0.1 A. The pump is delivering its usual flow, and the clamp meter is set to AC amperes. Before declaring a fault, how should the current measurement be corrected?
Correct answer: D - Close the jaws around one phase conductor at a time
The conveyor runs normally for as long as START is held, then stops immediately when START is released. Its three-wire control uses a momentary normally open START button, a normally closed STOP button, and a normally open M auxiliary contact wired across START. No overload trip occurs. Which fault best fits this symptom?
Correct answer: B - An M seal-in contact that fails to close
A 120 V control rung contains eight series contacts, S1 through S8 in that order, followed by an intact relay coil and return X2. All contacts should be closed; the only fault is one contact that remains open. Referenced to X2, the source reads 120 V, the point immediately after S4 reads 0 V, and the point immediately after S2 reads 120 V. Which two contacts still require isolation testing?
Correct answer: A - S3 and S4
After a reversing contactor is replaced, both FORWARD and REVERSE turn the motor clockwise. With the starter locked out, continuity tracing shows that both contactors connect L1 to T1, L2 to T2, and L3 to T3. Which correction restores opposite rotation while preserving the existing FORWARD direction?
Correct answer: A - Interchange only T1 and T3 at the reverse contactor's output terminals
A compressor stops when receiver pressure reaches its 120 psi cut-out setting. Pressure then falls to 105 psi, but the compressor remains off. The switch's cut-in setting is 90 psi, the pressure gauge is verified, and no protective device has tripped. How should this observation be interpreted?
Correct answer: C - Remaining off is expected within the switch's operating differential
A nonretentive on-delay relay is set to 8 seconds. Its input is ON from t = 0 to t = 6 seconds, OFF from t = 6 to t = 7 seconds, then continuously ON. The timed normally open contact closes at t = 15 seconds. A maintenance note calls this a seven-second timing error. Which explanation should replace that note?
Correct answer: B - The interruption reset the delay; eight continuous seconds elapsed after t = 7
A replacement variable-frequency drive (VFD) runs the motor correctly from its keypad but ignores the hardwired remote RUN switch. Its display shows READY, no active fault, a 35 Hz speed reference, and the remote RUN input changing state when the switch is operated. The active start-command source is KEYPAD. What must be corrected to restore remote starting?
Correct answer: A - Select the terminal block as the start-command source
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