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Air Conditioner Not Working? Replace the Run Capacitor

Updated on July 7, 2014
A typical A/C Unit
A typical A/C Unit | Source

Murphy's Law is Alive and Well

It is summer and hot here in California, especially where I live which is in the central valley area. For the past week, the highs have been in the three digit range. It is definitely hot. Fortunately we have a thing called air conditioner (A/C). When I turned mine on and waited several minutes for the nice cool air to permeate the first floor of my house, nothing happened.

Murphy's law is at it again. Just when I need it most, the A/C failed to work. As I scratch my head, the first thing that popped into my mind was the high cost of A/C repair. HVAC (Heating, Ventilation, and Air Conditioning) repairmen really make a killing during this time. They are in high demand and their schedule is always full.

As I headed outside to see my A/C unit, and passed through my garage to reach my backyard, I could already feel the hot air coming from the outside. Finally, I reach my A/C unit, and I see that the fan isn't even turning, but I can hear the compressor doing its work. Now what?

Google It

I am not a HVAC professional. As such, I really didn't know what to do when I saw that the fan isn't working. All I know is that the fan in the A/C unit is supposed to be turning in order to release the heat into the air. Since it was not, I knew the A/C unit was definitely broken.

Not really knowing where to start, I googled "air conditioner fan not working." After, doing a bit of searching and reading, the most common root problem that resonated on most of the online information was that the run capacitor is bad.

Finding the Run Capacitor

Having seen an HVAC professional open an A/C unit and explain roughly what was in it, I knew where to find the run capacitor and how it looked like. In most cases, there is an access panel to that part on the side of your A/C unit held only by a couple of metal screws. Once those two screws are removed, the metal panel covering the run capacitor will easily come off. From there, you should be able to see the run capacitor and what additional screws need to be removed to access the capacitor.

The defective run capacitor still plugged in
The defective run capacitor still plugged in | Source
Old run capacitor I extracted from my A/C
Old run capacitor I extracted from my A/C | Source


Make sure power to the A/C unit has been turned off before you attempt to remove the run capacitor. In addition, you'll need to discharge the capacitor by touching its conductors with another conductor so as to remove any electrical charge from it. Make sure the side of the conductor you are holding/touching is insulated; otherwise, you could be in for a shock.

Buying the Run Capacitor

Not wanting to spend a lot on repairing the A/C, I checked for a replacement part. The unit I extracted had the following specifications: 7.5uf, 50uf, 370VAC. These numbers represent the capacitance between the ground and the compressor, the ground and fan, and the voltage rating of the capacitor. If these don't make any sense, don't worry. You need only know these numbers so that you can find the correct one when you go shopping on line.

Now, I was able to find an equivalent unit for only $11.99. So I ordered it right away, and it arrived 2 days later--actually 1 day earlier than the originally projected 3 to 5 day delivery time.

Installing the New Run Capacitor

Before installing the replacement run capacitor, I made sure that power to the A/C unit was off. I reconnected the electrical wires using the labels on the run capacitor and the circuit diagram that I found on the panel cover. With all the connections snug, I replaced the panel cover, turned on the circuit power, and went inside the house to force the A/C to turn on.

Note that the run capacitor terminals are labeled with a C, FAN, and HERM. The C stands for common/ground. In my case, the yellow wires were my ground or common wires. The FAN connects to the FAN electrical wire, which in my case was the brown wire. The HERM is the connection that goes to the compressor, which was the blue wire in my case. If you make a mistake on the connection, your A/C won't work, so make sure the wires are connected to the correct terminal. The wiring diagram should be on the metal panel; look for the capacitor in the diagram. It is typically labeled "capacitor."

It Works

After turning on the A/C unit from within the house, I heard the fan immediately engage. I went to one of the vents and started feeling cool air once again.

I don't know how much HVAC folks charge now for labor, but I know labor is expensive. This self-help exercise really saved me a few bucks. The only thing I paid for is the run capacitor, which was only around $12. Not bad.

Have you experienced a similar problem? If so, why not share your experience with the rest of us?


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