Service Overview
- Average Cost: KES 1,500 – 4,000 per capacitor
- Replacement Time: 30-60 minutes
- Common Types: Start capacitors, run capacitors, dual capacitors
- Lifespan: 10-20 years under normal conditions
- Urgency: Immediate replacement needed to prevent compressor damage
Capacitors are among the most frequently replaced components in air conditioning systems, yet they’re often misunderstood by homeowners. These cylindrical devices store and release electrical energy to help motors start and run efficiently. When capacitors fail, your AC may refuse to start, run inefficiently, or shut down unexpectedly, making timely replacement essential for system health.
How Capacitors Function
Air conditioners typically contain two types of capacitors serving distinct purposes. Start capacitors provide the initial electrical boost needed to get the compressor or fan motor spinning from a standstill. These capacitors deliver a powerful surge of energy for just a few seconds during startup, then disconnect from the circuit. Run capacitors remain in the circuit continuously while the motor operates, providing a steady supplemental current that improves efficiency and motor performance. Many modern AC units use dual capacitors that combine both start and run functions in a single component, simplifying the system while reducing space requirements.
Recognizing Capacitor Failure Symptoms
Failed capacitors produce distinctive symptoms that help diagnose the problem. If your air conditioner hums loudly but won’t start, the start capacitor has likely failed, leaving the motor struggling without sufficient starting power. An AC that starts but runs weakly, cycles on and off frequently, or takes longer than usual to cool indicates a failing run capacitor. You might notice higher electricity bills as the motor works harder without proper capacitor support. In severe cases, the unit won’t respond at all when you turn it on.
Physical inspection reveals obvious capacitor failures. A bulging or swollen capacitor top indicates internal pressure buildup from component breakdown. Leaked fluid around the base, a burnt smell, or visible corrosion on terminals all signal immediate replacement needs. However, capacitors can fail internally without external signs, which is why technicians test them with specialized meters.
The Replacement Process
Capacitor replacement, while straightforward for professionals, involves potentially lethal voltages and should never be attempted by untrained individuals. Even after powering down the AC, capacitors retain electrical charges that can cause serious injury. Technicians begin by shutting off power at both the thermostat and circuit breaker, then use insulated tools to discharge any remaining energy stored in the old capacitor.
After safely discharging the capacitor, technicians photograph the wire configuration, noting which colored wire connects to each terminal. They then disconnect the wires and remove the mounting bracket holding the capacitor in place. The replacement capacitor must match specific electrical ratings measured in microfarads (μF) and voltage. Installing a capacitor with incorrect ratings can damage the motor or cause premature failure.
The new capacitor is secured in the mounting bracket, and wires are reconnected to their proper terminals. Technicians ensure all connections are tight and properly insulated, as loose connections create resistance that generates heat and leads to component failure. Some systems require multiple capacitors, and best practice suggests replacing all aging capacitors simultaneously rather than waiting for sequential failures.
Testing and Verification
After installation, technicians measure the capacitor’s actual output using a capacitance meter to verify it falls within acceptable range of its rated value. They then power up the system and observe the startup sequence, listening for smooth motor engagement without excessive noise or vibration. The AC should start promptly and run quietly with no hesitation. Temperature differential across the indoor coil is checked to ensure the system is cooling properly, confirming that the new capacitor is providing adequate motor support.
Preventive Maintenance and Lifespan
Capacitors typically last 10-20 years, but several factors affect their longevity. High ambient temperatures accelerate capacitor aging, which is why outdoor unit capacitors often fail sooner than those in climate-controlled spaces. Voltage fluctuations stress capacitors, causing premature wear. Running an oversized AC that frequently cycles on and off subjects capacitors to repeated stress from constant starting.
Regular maintenance helps maximize capacitor life. Annual professional inspections catch deteriorating capacitors before they fail completely, preventing secondary damage to expensive compressor motors. Keeping the outdoor unit shaded and ensuring proper airflow reduces heat stress on components. Installing whole-house surge protection shields capacitors from voltage spikes that cause instant failures.
Economic Impact
Despite being relatively inexpensive components, failed capacitors cause disproportionate problems. A compressor trying to start without proper capacitor support draws excessive current, potentially triggering circuit breakers and creating voltage drops affecting other appliances. If forced to run without adequate capacitor support, compressor motors overheat and can fail completely, leading to repair costs ten times higher than simple capacitor replacement. This makes prompt capacitor replacement not just a convenience issue but a critical preventive measure protecting your entire cooling system investment.
