Capacitor
Function
The capacitor in a refrigerator's electrical system serves as an energy storage device that provides additional starting torque and running efficiency for various motors, including compressor motors, evaporator fan motors, and condenser fan motors. Capacitors store electrical energy in an electrostatic field and release it when needed to create phase shifts in alternating current circuits, effectively improving motor performance and reliability. In refrigerator applications, capacitors help single-phase motors develop the rotating magnetic field necessary for efficient operation.
Start capacitors provide high-energy pulses during motor startup, delivering the extra torque needed to overcome initial inertia and accelerate the motor to running speed. These capacitors typically have high microfarad ratings but are designed for intermittent duty, operating only during the few seconds required for motor startup. Start capacitors work in conjunction with start relays that disconnect the capacitor once the motor reaches approximately 75% of rated speed.
Run capacitors, in contrast, remain connected during continuous motor operation to improve running efficiency, power factor, and starting characteristics. These capacitors typically have lower microfarad ratings than start capacitors but are designed for continuous duty throughout the motor's operating cycle. Some refrigerator systems use dual-purpose capacitors that serve both starting and running functions, simplifying the electrical circuit while providing adequate performance for smaller motors.
Symptoms of a Broken Capacitor
Capacitor failures produce distinctive symptoms that vary depending on the type of capacitor and the motor it serves. Start capacitor problems typically manifest as difficulty starting motors, with compressors or fans that attempt to start but fail to reach running speed. You may hear humming or buzzing sounds as the motor receives power but cannot develop sufficient torque to begin rotation. The motor may eventually start after multiple attempts or longer startup periods, indicating marginal capacitor performance.
Run capacitor failures often cause motors to run inefficiently, drawing excessive current and generating more heat than normal. Motors may start normally but run at reduced speed, operate noisily, or cycle on and off frequently due to overheating protection devices. You might notice increased energy consumption as motors struggle to maintain proper operation without adequate capacitor support.
Visual inspection sometimes reveals obvious capacitor problems such as bulging or swollen cases, oil leakage, or burn marks around terminals. These physical symptoms indicate internal failure and require immediate replacement to prevent further system damage. Failed capacitors may also cause circuit breakers to trip, fuses to blow, or overload protectors to activate repeatedly as motors draw excessive current trying to compensate for inadequate capacitor support.
Repair Solutions
Diagnosing capacitor problems requires careful electrical testing combined with visual inspection and operational observation. Before beginning any work, ensure the refrigerator is unplugged and allow adequate time for capacitors to discharge, as they can retain dangerous electrical charges even when power is removed. Never touch capacitor terminals with bare hands or tools without first discharging the capacitor safely.
Locate the suspect capacitor, typically mounted near the compressor or within the control compartment. Capacitors are usually cylindrical components with two or three terminals and are clearly marked with microfarad ratings and voltage specifications. Examine the capacitor visually for signs of physical damage, swelling, leakage, or terminal corrosion that indicate failure.
Test the capacitor using a multimeter capable of measuring capacitance, or use a dedicated capacitor tester for more accurate results. Disconnect all wires from the capacitor terminals and measure the actual capacitance between appropriate terminals. Compare the measured value to the capacitor's rated specifications, which should be within 10% of the labeled rating. Additionally, test for continuity between terminals and ground; any continuity indicates internal shorting and requires replacement.
When replacing a failed capacitor, use an exact replacement with identical microfarad rating and voltage specification. Installing a capacitor with incorrect specifications can damage motors or cause system malfunction. Mount the new capacitor securely in the same location as the original, ensuring proper ventilation and protection from moisture. Connect wires to the appropriate terminals, typically marked as C (common), FAN, and HERM (hermetic compressor), and ensure all connections are tight and properly insulated. After installation, test motor operation to verify proper starting and running performance.