Wear work gloves and use a screwdriver with an insulated handle so you don t shock yourself.
Testing start capacitor with resistor.
It s an all or nothing test that tells you if the capacitor is dead but it won t diagnose one that is still functioning weakly but about to stop working.
Symptoms include the hum of a garage door opener and its failure to start working or the failure of an air conditioner to cool the room.
Complete the circuit by connecting a power supply of known voltage.
Many single phase compressors require a start capacitor to assist in starting the motor.
Start capacitors are not designed to dissipate the heat associated with continuous operation.
Test a capacitor using continuity test.
Overheating is a primary cause of a failed start capacitor.
A multimeter is an essential tool required to test a capacitor various methods of capacitor test using multimeter are discussed below.
You can use an ohm meter to test a capacitor.
A start capacitor resistor also called a bleed down resistor is used to bleed off residual voltage in a start capacitor after it has removed from a motor circuit after start up.
Connect a known resistor typically a 10 kω resistor in series with the capacitor.
Turn on the power supply and measure the time taken for the capacitor to charge to 63 2 of the supply voltage for example if the supply voltage is 12v then 63 2 of this is around 7 6v.
Then use a screwdriver to open the appliance so you can locate the capacitor which is a metal tube that should be near the motor.
These capacitors will occasionally fail causing a compressor to fail to start.
Not all start caps use resistors as there are other ways to accomplish the task of reducing residual voltage in a capacitor.
Understand what a run capacitor does the run capacitor provides continuous phase shifted current to the motor start winding allowing the motor to run with the design efficiency in the right direction with the appropriate torque with near unity power factor power factor near 1 0 if the run capacitor is failed often the motor.
Remove the suspicious capacitor from its circuit.
Check test a capacitor using analog multimeter test check a capacitor with a digital multimeter checking capacitor by multimeter in the capacitance mode check and test a capacitor by simple voltmeter traditional method to test check a capacitor find the capacitor value by measuring the value of time constant.
This one covers testing of the start capacitor.
What is important to note is that if the capacitor you are replacing had a bleed down.
This video is part of the heating and cooling series of training videos made to accompany my websites.
Discharge it using a resistor.
The continuity test method for a capacitor shows whether it is opened short or good.
Set the multimeter in continuity mode.
