3 Common Causes For Malfunctioning Evaporator Coils And Lack Of Cold Air

by Claude Walters

The evaporator coils in a central air conditioner are one of the last, but most important stops in the cooling process. Liquid refrigerant passes from the condensing unit outside your home and into the evaporator coils in the air handler. The evaporator coils turn the refrigerant back into a gas and, in the process, the coils become cold. Cycling warm air, passing through from your home via a blower fan, passes over the coils and becomes colder, then passes back out into your home.

Problems with the evaporator coils are a common reason for the sudden loss of air conditioner efficiency. If your unit has recently stopped cooling as effectively or stopped cooling completely, a check of the evaporator coils is in order. You can perform the basic checks and maintenance by yourself, but call in an HVAC technician for assistance for the more complicated tasks.

Here are a few of the common causes of malfunctioning evaporator coils and how you can spot and fix the problems.

Dirt Buildup

Malfunctioning evaporator coils could simply be dirty. Surface dirt interferes with the chemical reaction and can leave the coils less cold than required to cool your home. Dirty coils are one of the easiest problems to fix if you know how to access your evaporator coils or have your owner's manual to help you find the coils.

Turn off all electricity to the unit before working, and remove the rear panel to gain access to the coils. Apply a no-rinse foam cleanser to the coils, making sure to follow the package directions on both application and required setting time. Once enough time has passed, you can check the coils to see if the cleaner did its job.

If there's a bit more surface dirt, you can gently try to scrape it away using a stiff cleaning brush. Dirt that refuses to come off might need a professional cleaning, or the coils might need to be replaced, so call in an HVAC tech for help.

Bent or Broken Coils

When you examine your coils, if you see a section of coils that are bent or broken, you should abandon the project immediately and call in an HVAC tech. Bent coils will need to be replaced by a professional. Broken or cracked coils could be leaking refrigerant, which is a potentially hazardous chemical when not handled properly.

Leave the power off to your unit until the tech comes so that more refrigerant doesn't cycle through and become stuck behind a bend or leak through a crack.

Low Refrigerant

Do the coils look perfectly fine upon inspection? Are you sure the compressor pump is firing up in the condensing unit and the fan in that unit is operating? Is the fan operating in the air handler? If everything else looks find, you might simply be low on refrigerant. HVAC techs are typically the only people legally allowed to purchase and administer refrigerant, so this is another job to leave to the pros.

For more information and tips, contact a local HVAC company like Hudson Hdwe Plumbing & Heating Inc​.