The Overcharged or Undercharged AC: Why You Don't Want Either!

air-conditioning-manometer-pressure-refrigerantWhat does an overcharged or undercharged air conditioning system mean?

It doesn’t have anything to do with price, and it isn’t electrically charged the way a cell phone or other mobile device is charged. The “charge” in this case refers to the amount of chemical refrigerant circulating inside an AC system.

  • Too much refrigerant: overcharged.
  • Too little refrigerant: undercharged.

To understand why either situation is a serious problem, we have to explain a bit about refrigerant.

Refrigerant Should Be at a Set Level for an AC

Refrigerant is an essential part of how an air conditioner works. The chemical blend goes through a process of evaporation and condensation, phase shifting between liquid and gas, to absorb heat from inside the house and then exhaust it outside.

As the refrigerant moves between liquid and gas, it doesn’t get used up, so the same amount of refrigerant in an air conditioner should last for the life of the system. That specific amount of refrigerant in an air conditioning system that allows it to work is called the system’s charge. If an AC has more refrigerant or less refrigerant than the factory set amount, the system is said to be overcharged or undercharged.

Both situations are bad news for an air conditioner.


An air conditioning system can become overcharged because of amateur repair work or misunderstandings about what refrigerant is. A non-professional may attempt to “fix” an AC that’s losing cooling power by putting in more refrigerant, even if low refrigerant has nothing to do with the problem. This will end up wrecking the air conditioner because it changes refrigerant pressure throughout the system and allows liquid refrigerant to flood into the compressor, causing it to fail.

Make sure you only have professionals repair your AC to avoid this. If an air conditioner is overcharged, a certified technician can bleed out the excess amount and repair anything that’s been damaged.


An undercharged air conditioner is more common and occurs because leaks have started along the copper refrigerant lines, allowing the refrigerant to escape. This can happen slowly without a homeowner at first noticing anything wrong. But things will soon go wrong: the AC will start to lose its cooling power, the evaporator coil will begin to freeze over because there’s no longer sufficient refrigerant to warm up the refrigerant that’s remaining, and eventually the compressor will overheat and fail.

At the first sign of a problem, such as ice on the coil, an AC that can’t keep up with the heat, or a hissing sound (escaping gaseous refrigerant), call for repairs. The leaks need to be patched and the correct amount of refrigerant added back by a professional.

Call for HVAC Experts

To deal with refrigerant on any level requires a licensed professional. Make sure you only call for professional repairs for your air conditioning in Concord, MA, when anything seems wrong. We’re your certified AC repair experts in the MetroWest Area to handle cooling system troubles.

Get on repairs for your air conditioner fast with a call to our experts. Basnett Plumbing, Heating & AC has been trusted for over 30 years.

Need HVAC Service?

Contact the experts at Basnett Plumbing, Heating, AC & Electrical.
Call us at 978-431-2906!