To test the capacitor with a multimeter , set the meter to read in the high ohms range, somewhere above 10k and 1m ohms. Touch the meter leads to the corresponding leads on the capacitor , red to positive and black to negative. The meter should start at zero and then moving slowly toward infinity.
Most digital multimeters use a symbol similar to –|(– to signify capacitance. Move the dial to that symbol . If several symbols share that spot on the dial, you may need to press a button to cycle between them until the capacitance symbol appears on the screen.
The most common problem that bad capacitors can cause is “hard starting.” This is when the compressor of an AC has difficulty starting up, stutters trying to turn on, and then shuts off a short while later. Before a capacitor fails , it may start begin to make a clicking noise.
The most common signs and symptoms of a bad AC capacitor include: AC not blowing cold air. AC takes a while to start once you turn it on. Humming sound coming from your air conditioner.
The voltage classifications are 370V and 440V. Capacitors with ratings above 70 microfarad (uF) are starting capacitors . Run capacitors are designed for continuous duty, and are energized the entire time the motor is running . Single phase electric motors need a capacitor to energize a second phase winding.
Overheating is a primary cause of a failed start capacitor . Start capacitors are not designed to dissipate the heat associated with continuous operation; they are designed to stay in the circuit only momentarily while the motor is starting . If a start capacitor stays in the circuit too long, it will overheat and fail .
If the capacitor does not show any sign of continuity , the capacitor is open. If the multimeter beeps continuously, the capacitor is short and needs a replacement.
A higher voltage means the electricity is being pushed harder. Voltage is measured in volts. The symbol for volts is V. Resistance is measured in ohms. The symbol for ohms is Ω (the capital Greek letter omega).
The amount of storage capacitance is measured in farads. Capacitors are usually measured in units of micro-farad. Displayed as μF F, mfd, MFD, MF and UF, micro-farad measurement on a multimeter is usually indicated by “MFD.” Compare the measured MFD with the capacitors expected MFD measurement.