Edit ArticleHow to Check a Start Capacitor Start capacitors are common in home appliances and all sorts of HVAC equipment. If the motor on your washer makes a humming noise, but it won't start, check the start capacitor. You can perform a simple test to tell you if your capacitor is completely dead or if it still has some life left in it. See Step 1 for more information. Remove the start capacitor. The easiest and most convenient way to discharge the capacitor is to attach the terminals of a low wattage 120v light bulb (about 20 watts) to the capacitor terminals. This will safely discharge the electricity which may still be stored into it. Be very careful that you do not short the terminals by connecting one to the other, until after the capacitor has been discharged. Doing so could injure or kill you. Use extreme caution when discharging the capacitor before proceeding. Examine the capacitor for bulging or fluid. Signs that the top of the capacitor are bulging out slightly, as if expanding, is a sign that the capacitor might be dead.

Likewise, check and look for any dark fluid that appear on the top of the capacitor. If you see either of these, it's still a good idea to run the check with a voltmeter, since it only takes a few seconds. Use an analog or digital volt meter. Both work in essentially the same way and are both appropriate for the job. Set the meter to 1k ohms to begin the test. Touch the two terminals with your ohms meter test leads. The basic check involves touching the test leads twice and comparing the reaction. Touch the test leads to the terminals and then reverse them. The needle in your meter should swing to 0 ohms and swing back to infinity on an analog meter, and should display open line every time that you reverse on a digital meter. If it does, you've got a live capacitor and your problems are elsewhere. If there is no difference the capacitor is dead. Check for capacitance, if the capacitor is alive. If you have a multimeter, you can use the capacitance setting to perform a quick check.

If the number is relatively close to the number listed on the capacitor, it's in good shape. Make sure that you discharge the start capacitor's electricity before doing any test on it. The way you do this is to take a metal object that has an insulated handle on it, such as a screwdriver. While holding the insulated end place the metal end across the contacts on the capacitor, and hold it for a few seconds. how to clean the coils on a window ac unitThis will discharged the capacitor so you can handle it without being shocked.unit consumption of 2 ton ac The above tip to discharge the capacitor by shorting the terminals is a bad idea as the article warns against doing. how to wire a hvac unitShorting the terminals of a fully charged high voltage capacitor will result in a very large current flow through the capacitor.

That can result in the capacitor exploding. Imagine the results if you are holding the capacitor in your hands. Start capacitors store electricity on them; that is why you need to discharge them. If the capacitor is a large one meaning the larger the micro-farad number is the more electricity/energy is stored. So the more energy that is stored the more severe burn you will get!Air conditioners work hard to keep you cool, and you don't realize how much you rely on them until you are stuck in a sweltering room with no relief. If your air conditioner suddenly goes out, there is no need to panic. Follow these simple steps to bring your A/C unit back online and you may avoid the need to call in an expensive professional.Many thermostats are battery-operated, and once they power down so will your air conditioner or heater. Check that your thermostat is fully operational and the connections to the wall are good.Check Fuses and Reset ButtonsUnder a heavy load, an A/C unit can trip an electrical breaker.

Check the breaker box to make sure this hasn't happened, and also use a multimeter to check the fuses inside the disconnect block next to your air conditioner to make sure they are still functioning. If either of these scenarios appear, there could be an underlying electrical problem with your home's main box. Have an electrician look at that.It can take 15 to 20 minutes for your air conditioner to get up and running after it's tripped a circuit breaker or the power is turned off. Be patient and wait it out before trying something else.A clean filter is vital to a well-functioning air conditioner. During the summer it is good to check your filters once a month. If you have pets, leave windows and doors open, or have allergies, you may need to change your filter more often.A blocked or dirty air condenser can also degrade the performance of your unit. Make sure the vents around your air conditioner are clear of debris and the area surrounding your A/C unit provides plenty of air flow.Turn off the power at the main box to the A/C unit and open the electrical access panel on the air conditioner.

It is usually located where the electrical power comes into the unit. Check for rodent nests and wires that have been chewed or frayed.Now we're getting into more serious stuff. The contactor is a relay that converts the low-voltage signal from the thermostat into a signal to switch on 220V power to the compressor and condenser. When these contactors fail, the A/C unit will go down. They are a cheap and easy to replace. Check the owner's manual to locate the contactor and replacement model.A capacitor stores electricity and is used during the compressor and fan startup for extra power. It also protects the motor from damage due to fluctuating voltage. These capacitors don't last forever and can go out unexpectedly. If you are comfortable with electrical repairs you can use a screwdriver to discharge the dual start/run capacitor by connecting terminals to short it out, and then replace it with a new one made for the make and model of your A/C. If that's beyond the level of DIY you're comfortable tackling, then call a pro.