Prepping for summer: how to clean a central air conditioning unit

July 28, 2015

With summer coming, it's never too early to get your central air conditioning unit ready by giving it a good clean – to help keep you cool all summer long. Here's how to get your central air conditioning unit primed for the hotter months ahead.

Prepping for summer: how to clean a central air conditioning unit

How to turn your thermostat to cool

When it's time for your central air conditioning system to come out of hibernation – or even after a prolonged in-season shut down for maintenance or repairs – it's essential to power it up properly. Why? Because the surge of electricity caused by suddenly restoring the power could potentially damage the unit's compressor.

To do this:

  1. First, make sure the thermostat is switched to the "off" position. Also, ensure that the system is not set to heat or cool.
  2. Next, restore power and allow the system to run for 24 hours, with only the fan going. This way the compressor's lubricant will have a chance to warm up before use.
  3. Finally, you can switch your thermostat to the "cool" setting and adjust it to the desired temperature to activate your air conditioner.

If ever there's a brief power interruption while the air conditioner is on, or it is accidentally turned off, switch the thermostat to "off" and keep it that way for at least five minutes before restarting the system.

Cleaning the air conditioning unit

A clean air conditioner runs more efficiently and can help you save money. It's also an opportunity to look for any mechanical issues before they become bigger problems including leaking fluids, worn gaskets and missing clamps.

Although cleaning a central air conditioning unit takes more than a few minutes, the task is simpler than it might seem.

To begin the cleaning process:


  • Turn off power to the air conditioner, as described above.
  • To access the condenser coil and its fins, you may have to remove a protective metal housing that covers the unit. (If there is a housing on your particular air conditioner, it's usually screwed or bolted in place at the base.)


  • Vacuum the condenser coil's fins with a soft-bristle brush attachment. Be careful not to bend or distort any of the delicate fins as you go. Use a fin straightener comb, sold at HVAC parts suppliers, to straighten any bent fins you encounter.
  • Remove leaves and other debris surrounding the coil that could potentially block airflow.

Have a friend assist you with this stage. The unit's fan and motor are usually attached to the housing, which needs to be supported carefully to avoid straining electrical wires and connections.


  • Take a garden hose equipped with a trigger-controlled nozzle and spray the fins from the inside out, moving around the perimeter of the condenser to clean the entire coil. Remove any debris that has accumulated on the inside and at the bottom of the condenser unit.
  • Oil the motor at its ports (if any) with either a manufacturer-recommended lubricant or 20-weight machine oil. Replace the housing.


  • Restore power and set the indoor thermostat to "cool" so that the compressor comes on. Listen for any noises that might indicate trouble.
  • After 10 minutes, feel the tubes that carry refrigerant to the unit: the uninsulated one should be warm to the touch and the insulated one should be cool.

A central air conditioning unit is a major investment and keeping it clean will help to ensure it runs flawlessly through the hotter months of the year. However, should you spot any issues that appear to affect how well your air conditioner is running have a certified technician take a look at it.

The material on this website is provided for entertainment, informational and educational purposes only and should never act as a substitute to the advice of an applicable professional. Use of this website is subject to our terms of use and privacy policy.
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