If you have a Philips HeartStart OnSite (HS1) or FRx AED mounted on your wall, you are probably used to seeing a reassuring, blinking green light. But what does it mean when that green light suddenly turns into a flashing red “X”, accompanied by a loud, repeating chirp?

For many facility managers and safety coordinators, seeing the red “X” causes immediate panic. However, a red “X” does not mean your AED is permanently broken. It simply means the unit’s internal computer has failed a routine self-test and is no longer Rescue Ready.

Here is exactly how to troubleshoot the red “X” and get your Philips HeartStart back in service.

Step 1: Do Not Ignore It

A flashing green light means your AED is ready to save a life. A flashing red “X” means the device has detected an error that could prevent it from delivering a shock during a cardiac emergency. If you see the red “X”, the AED must be serviced immediately.

Step 2: Press the Blue “i-Button”

You don’t have to guess what is wrong with your Philips AED. The device is designed to tell you exactly what the problem is.

Look for the blue “i-Button” (Information button) on the front of the unit. When the unit is chirping and flashing the red “X”, this blue button will also flash.

• Press the blue button once.

• The AED will speak out loud and tell you the exact cause of the failure. (e.g., “Battery low,” “Replace battery,” or “Pads missing”).

Step 3: The Most Common Culprit (Low Battery)

If the voice prompt tells you the battery is low or depleted, the unit has reached the end of its standard 4-year standby lifespan. When the battery drops below a critical threshold, the unit will purposefully disable itself and display the red “X” so you don’t take an underpowered machine into a rescue.

To fix this, you must install a fresh Philips HeartStart M5070A Replacement Battery.

Once the new battery is clicked into place, the AED will automatically run a comprehensive self-test. Once it passes, the red “X” will disappear, the chirping will stop, and your unit will return to a flashing green light.

Step 4: What If the Voice Prompt Says “Pads”?

If you press the blue button and the machine says something about the pads, your battery might be perfectly fine.

• Check the Connection: The pads connector must be firmly plugged into the AED at all times. If it gets knocked loose, the red “X” will appear.

• Check the Expiration: Philips SMART Pads expire every two years. The AED can sense if the gel is drying out or if the pads have been compromised.

If the pads are the issue, simply plug them back in, or order a replacement set of Philips adult SMART pads to clear the error.