Air-conditioning systems in the process, the timely replacement of old capacitor is necessary. This article describes how to check and replace the air conditioning system of a motor capacitor.

First, we need to understand the composition of air-conditioning outdoor unit
the condenser outdoor unit consists of a fan, coils, cooling fins, a hermetically sealed compressor, electrical contactor and capacitor.

Second,we need check the condenser outdoor unit Problem
Neither the fan nor the compressor were running. But I could hear a distinct electric humming noise. I put my hand on top of the unit’s housing where the fan motor is mounted and it felt uncomfortably hot. The compressor was also turned off in thermal overload mode.
 
After doing some online research I suspected that the symptoms of the problem with my air conditioner pointed to a faulty “dual motor 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. If the 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.
 
Once I was 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 easily see the 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.

I checked the single pole contactor for any insects, bugs or ants stuck in between the silver contacts but it seemed to be clean and working correctly. Anything 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. Be 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 capacitors they will have 3 terminals. The terminal labeled “HERM” is for the yellow wire that goes to the “Hermetically Sealed” compressor. 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 capacitor.

Third,Air conditioner outdoor unit to find the reasons for not working, replace the motor capacitor

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 handle. 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.

 I installed my shiny new 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. With sweat on my forehead I rushed inside, flipped the breakers back to “ON” and switched the thermostat down to “Cool”.

it is OK and sound of the compressor and fan start outside and within a few seconds the A/C vents started to blow refreshingly cold air.