Air conditioner (A/C) troubleshooting tips

Last updated on March 10th, 2024 at 03:19 pm

The number one cause of air condioner problems is compressor failure. When this happens, a professional needs to contacted to replace the compressor. However, many other air conditioner problems are a little simpler and easier to troubleshoot.

But a dirty filter can make the unit behave like there is a compressor problem. When the filter is dirty and air flow into (and our of) the unit is severly limited, in most air conditioners the compressor will not turn on. This is because there is insufficient circulation for proper efficient operation. And the remedy is simple – clean or replace the filter. If you turn on the A/C but the compressor doesn’t turn on (and it should), check the filter.

If the filter is clean, but the compressor does not turn on, adjust the thermostat down. A compressor won’t turn on unless it absolutely has to – this is by design to save energy. If the temperature difference between what is in the room and what is programmed in the thermostat isn’t great enough, the compressor won’t operate. Test this by lowering the temperature of the thermostat.

If the compressor still doesn’t operate, but the fan is running, check for an obstruction in the unit. Most of the time you can see through the unit to the coils and compressor. If that fails, consider calling a professional.

If the temperature or thermostat seem to be off, check the temperature probe. Usually, this is housed behind the filter in front of the compressor coils facing the room. If it is loose or appears to be damaged, it will give incorrect readings and will result in malfunction.

If you find the a/c is running too long or often, take steps to make the room cooler. Draw shades, remove or avoid using heat generating appliances, etc. Also check the thermostat or thermometer probe to make sure it is working. Verify the air temperature of the room.

If the unit refuses to operate, make sure it is plugged into a grounded outlet. If it still does not turn on, check to make sure the safety plug hasn’t been tripped. Try moving the unit to a different outlet. Also, check your fuses and breakers. Some older units may have a fuse built in – you can check this out as well. They are usually behind a control panel, or easily accessible via the filter removal panel.

If the unit makes a lot of noise or tends to rattle, there may be something in the unit. See if you can see anything foreign in the chamber near the fan or compressor housing. Usually, peeking through the filter grate and top vents will let you see through the unit. Also, if the unit is not securely attached to the window, the unit and window will rattle – especially when the compressors (at the bottom of the unit) kicks on. Secure with screws and if necessary reseat the unit so it sits flush to the window sill. Loose, old windows are notorious for this. Unfortunately, short of replacing the window there isn’t a lot you can do to buffer up the bad window.

Another common problem is for the foam inside the unit to become loose, damaged or cracked and fall into the unit. This results in a noticeable sound, sometimes even a whistle, coming from the unit. Simply remove the foreign object.

Of course, if you’re ever going to venture into the a/c unit, unplug the power! And be careful you don’t void any warranties.

If the air coming out of the unit doesn’t seem cold enough, verify the thermostat setting. Also, check the fan speed and make sure the filter is clean. A dirty filter will always reduce the effectiveness of an a/c unit. Check to make sure nothing is obstructing the heat exchanger outside. If all this checks out, the unit may need refrigerant added. Contact a professional and explain the situation.

If you determine at any time that a professional is needed to come out to your house, make sure you tell them the troubleshooting steps you’ve taken thus far. It helps them and may even save you some money by cutting the repair time!

2 thoughts on “Air conditioner (A/C) troubleshooting tips

  1. Thanks, some great tips for homeowners and do-it-yourselfers. I also highly recommend getting a biannual maintenance check-up on your system. these are fairly cheap (much cheaper than a service or repair call!), will save money on energy bills, and can extend the life of your AC by years. For some more tips on extending the life of your AC and saving money with your AC, appliances, and water heater, check out our blog post. Feel free to borrow any tips that might help your readers!

  2. I sure wish I could figure my problem out. I have no cool or heat with this window unit. I bought both and used 1 summer and 1 winder. They both quit this year in late spring. The compressor will not come on and the heat will not come on. They are only a year old. Does anyone have an idea?? It is a frigidaire Model FRA25ESU216…..

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