How to test a capacitor: disconnect
First step to test a capacitor, disconnect it…. And to unplug it, you have to find it. The capacitor is a component that stores electrical current before returning it to a motor to facilitate starting or to stabilize the current during operation. In summary, it is therefore connected to the engine. But beware, we are talking about electric current! Before looking how to test a capacitor, we equip ourselves to avoid electrocution: we start by unplugging the device concerned and we don't touch anything without insulating gloves. Once the small cylinder of the capacitor identified, we take a photo of the circuit to be able to reassemble it identically. The component of the circuit is then gently separated using an insulated clamp.
How to test a capacitor: discharge
After having removed the capacitor, it is discharged to avoid any risk of electric shock: it is enough to put its two or four poles in contact with a metallic object like scissors or a screwdriver. The risk is in principle eliminated, but it is better to keep the gloves if possible, in case a residual current remains in the capacitor. It is done ? We go to the multimeter!
How to test a capacitor: calibrate
When we search how to test a capacitor, the shortest answer is ... with a multimeter, won. For those who do not master, it is the most basic electrical measuring device of the panoply. It is adjusted according to the ohmmeter function, the one that tests the continuity of the capacitor, in other words its proper functioning. Note that an automatic multimeter will take care of the adjustment itself, but with a conventional multimeter, it will be necessary to adjust the calibration. In this case, we base ourselves on the capacitance of the capacitor to be tested or, failing this, we opt for the highest rating.
How to test a capacitor: connect
This time everything is ready. Just connect the multimeter to the component to test the capacitor, the red tip of the multimeter on the + of the capacitor, the black tip on the -. Depending on the capacitor models, the sign can be located directly on the capacitor body, on a wire, on a pin or on a terminal. And if no sign differentiates the poles, it remains only to test them one after the other, by discharging the component again between each test, to find out how to test the capacitor !
How to test a capacitor: interpret
Once the multimeter is properly connected, numbers will appear on its screen. If the device is not digital, its needles move. In both cases, a working capacitor increases the measurement to 10,000 or more before falling back to 0. We are not panicking, the values may need several seconds to vary. On the other hand, if nothing moves after a minute or if the numbers or the hands remain blocked on the high value or the zero, the capacitor is defective. As for the subtleties, if the capacitor remains blocked on zero, it is that it is not supplied. If the value decreases without reaching zero, it has leaks. And if it gets stuck at the top, it just doesn't work. Whatever happens, the result is the same, it will have to be replaced!