If you have a newer HVAC system, you may have noticed a circuit board with visible LEDs. Although designs vary between manufacturers, you can usually find this board behind a plastic or glass panel, allowing you to see the integrated diagnostic lights. These LEDs provide you with information about the current status of your air conditioner and can alert you to potential trouble.

Under normal conditions, you should see at least one light illuminated on the control board. No light typically indicates that the system doesn't have power, which might be a problem if you haven't disconnected it or physically switched the unit off. Other patterns exist for various operation states, and you can learn a bit about them to understand your HVAC system better.

Locating Your Diagnostic Lights

While many newer units use a transparent panel to make it easier to read diagnostic codes, some manufacturers still place their circuit boards behind a solid door. If you don't see any diagnostic lights on your HVAC unit, start by consulting the manual for your system. You should be able to use this information to locate a circuit board door.

Note that disassembling any part of your HVAC system is not something you should attempt if you aren't comfortable with do-it-yourself work. Although there shouldn't be any problem with removing the circuit board access door, always proceed with caution. Once you have the door off and see the circuit board, avoid touching or moving anything inside the panel.

Reading Your Diagnostic Indicators

If you've ever worked on a home computer, you may be familiar with the concept of diagnostic LEDs. Your air conditioner's control board will have one or more of these LEDs. If you look closely, you should see labels near each light. For example, Rheem boards typically use the DS1 and DS2 as identifiers on their diagnostic lights.

You'll need your HVAC system's manual to glean any information from the pattern on the lights. In most cases, you'll need to count how many times each light blinks and compare that to a chart in your user's guide. If the lights are off or not flashing, it may indicate that the system doesn't have power or that there's currently no fault.

In general, you should only use this information to understand more about how your air conditioner functions. If your diagnostic lights indicate a problem, it's usually a sign that your system has shut down to protect itself. Consulting with a trained HVAC professional is the best way to diagnose the problem further and ultimately fix your home's air conditioner.

If you have an issue with your AC, contact a local air conditioning service professional to get help.