This capacitor testing guide will show you how to tell if a run capacitor requires replacement. Although the parts are relatively inexpensive, calling a repairman to diagnose and replace it would cost over $100. With this guide, you can keep that money.A capacitor is an electrical device that stores an electrical charge. They are used on fan motors and compressors in hvac systems.They have two electrical ratings. The first rating is the unit's capacitance which is given in microfarads (mfd). This is a measure of the amount of charge the unit can store with a specified voltage applied. The second rating is a voltage rating which tells what supply voltage the unit is rated for. This is usually 370vac or 440vac in hvac systems. This is important to know because, if a significantly higher voltage is applied, the capacitor will prematurely fail. There are two different types of capacitors which are used in hvac units. The first type is called a run capacitor and is used in furnaces, air conditioners, and heat pumps.

These capacitors are used with fan motors and compressors. They maintain a relatively constant voltage supply to these motors and increase their torque at startup.The second type is called a start capacitor. They are used in some air conditioners and heat pumps. They provide extra torque at startup for the compressor. A potential relay automatically disconnects them from the compressor after the compressor starts. For capacitor testing, a multimeter is required. Some digital meters have a capacitance setting. First the power supply should be shut off then the two terminals on the capacitor should be shorted across with a screwdriver. This will discharge the unit so you do not receive a shock. Disconnect the wires from the capacitor. Then, the leads of the meter are placed on the terminals and a reading is obtained. The reading you get should be within 6% of the rating on the capacitor. If your reading is more than 6% lower than the rating, the capacitor should be replaced.If you have an analog type meter, the capacitor is checked with the meter set to measure resistance.

Shut off the power, discharge the capacitor, and disconnect the wires attached to it. Then with the meter on the highest resistance setting, put the leads on the capacitor terminals. The resistance reading should start at zero and go up to maximum.Some obvious signs that the capacitor is bad are bulging of the unit or an oily substance leaking from it.price of new hvac unitYou can watch our video below that will show you how to test a run capacitor. carrier thru wall ac unitsIf you wish to have your own copy of our videos, you can purchase our training videos on DVD. dual split system air conditioner priceOur training videos walk you step by step through furnace and/or central air conditioner diagnosis and repairs. To find the proper replacement part, you can look for the ratings on the existing part.

You should find a voltage rating (either 370 or 440) and a microfarad rating. You can purchase your replacement part through our parts store.After your capacitor testing has shown that you have a faulty part, the replacement procedure is simple. If you have a dual run capacitor (the capacitor has three terminals on it), then you should mark the wires and write down where they go. Then simply disconnect the wires, replace the faulty part and then reconnect the wires.This guide is meant to assist residential home owners in troubleshooting any HVAC capacitor problems with their split unit air conditioning system. One hot South Florida afternoon I noticed that our A/C was blowing warm air out of the vents (a.k.a. "registers"). So I began the process of figuring out what was wrong by going outside to check on the condenser unit. The condenser outdoor unit consists of a fan, coils, cooling fins, a hermetically sealed compressor, electrical contactor and a dual start capacitor.

Neither the fan nor the compressor wereBut I could hear a distinct electric humming noise. hand on top of the unit's housing where the fan motor is mounted and itThe compressor was also turned off in thermal After doing some online research I suspected that the symptoms of the problem with my air conditioner pointed to a faulty "dual motor run/start capacitor". To be sure, I used a stick to give the fan blades a jump start in the correct direction. Sure enough the fan blades easily began to spin and the motor quickly revved up to normal speed but I still couldn't hear the compressor making any noise. I checked inside and the A/C was still blowing warm air but slightly less hot than before. fan blades on your motor won't spin at all or take a lot of force to move them, your fan motor has seized and probably needs to be replaced. convinced that my MARS GE (General Electric) air conditioning system needed a new combination or "combo" capacitor to help the condenser fan and

compressor get the kick start of alternating current electricity that they needed to operate, I pulled the fuses. Don't let your AC unit just sit there humming and building up heat if your unit has the same problem, at least turn it off at the thermostat and then turn off the power at both the breaker box and condenser fuse box if you're going to open the case. To access the electrical panel I had to remove the top cover where the fan is attached using an 8mm socket (or flat head screwdriver), lift it slightly off to the side and then take out two more screws on the bottom of the condenser unit housing. With that side panel off I could electrical contactor and the old capacitor. It's a sure sign that your capacitor needs to be replaced when it looks disfigured, bent, bulging, popped, or is leaking an oil like or greasy substance. single pole contactor for any insects, bugs or ants stuck in between the silver contacts but it seemed to be clean and working correctly.

stuck in the contactor can cause the outdoor A/C unit to stay on even when you turn it off at the thermostat. The indoor evaporator unit and blower will stop but the condenser outside will remain on because the contactor may have welded itself in the on position. The old capacitor was very swollen and looked like a soda can that had been repeatedly shaken up. sure to write down which wires go to what terminal on your capacitor before removing the old one or just take a few pictures. For home air conditioning systems that use dual run/start capacitors they will have 3 terminals. terminal labeled "HERM" is for the yellow wire that goes to the The "FAN" terminal gets connected to the brown wire that goes to the condenser fan. Finally the "COM" terminal is for the purple and red wires that go to the contactor and provide power to the Before you remove the old capacitor, you must discharge the stored electricity or you could be shocked!

There are several ways to accomplish this task. You could use either a 100 watt light bulb wired up to alligator clips, a 20k to 100k ohm resistor also wired with alligator clamps or just a large screwdriver with an insulated I opted for the screwdriver capacitor discharging method with rubber gloves added for extra safety. Luckily my capacitor wasn't holding a charge so there weren't any dramatic screwdriver welding sparks or loud electrical pops with bright flashes of arching lightning bolts. Can you tell that I was just a little bit disappointed? sure that the old capacitor is discharged of all electricity, short each of the terminals across each other and also to the metal lip on the body. you can gently wiggle loose and remove the HERM, FAN and COM wires. old part in hand, I took a trip to my local air conditioning supply warehouse to buy a new capacitor. For those of you living in South Florida, I can recommend ASAP Appliance Parts Inc. located at 1100 N. Florida Mango Rd.

Suite "H" in West Palm Beach, FL 33409. My old capacitor was a 370 VAC 60 HZ unit which they didn't have an exact match for but they said that it was perfectly fine to replace it with a higher voltage 440 Volt The total cost with sales tax was $31.84. less expensive than the $150 to $250 or more that a professional HVAC company (heating, ventilation, & air conditioning) technician would have charged me for the service call, the part and labor. round combination capacitor by tightening the metal strap bracket and hooked up the Herm, Fan and Com wires to the correct terminals which had those words stamped into the metal on top of the part. Then I confidently closed up the condenser electrical access panel, and replaced all the screws that hold the roof of the unit in place. Finally I pushed the fuses back in and closed the fuse box lid. If you haven't done it in a long time, now would be a good time to clean or change the