Security & Fire Protection Systems/Napco XP600


Having problems trying to figure out the reason the XP600 is showing AC Fail. The alarm came with the house 5 years ago. I have changed the battery out and reset the system. I am getting a AC fail when I check the trouble light. I used my meter to find out the voltage coming from the transformer (19.26V). The battery reads 12.68V. I have read the instructions and have hard booted the system - removing the transformer from the outlet and disconnecting the battery. Can you give me anything else to try to clear the alarm?

Hello Michael, and thanks for writing.

This panel is a little tricky when it comes to reporting system trouble, so I just want to ensure you're interpreting the trouble condition correctly.

It's a combination of how many times the sounder beeps along with which zone LED is illuminated. So when you press the SYSTEM button, check to see which zone -- 1 through 4 lights, along with the number of times the keypad beeps.

AC Power is one beep with zone one illuminated, low battery with zone 2 illuminated, communication failure with zone 3 illuminated, and telephone line failure with zone 4 illuminated.

I'd suspect either zone 3 or 4 in your case, since you've checked AC power and the battery. And if the previous owners had a monitoring service, they would have cancelled it, and that would cause a failure to communicate.

Or, if you discontinued land-line phone service in favor of cellular, then the control would report a "cut" phone line.

If none of this turns out to be the cause, consider that your control dates back to the late 1990's -- and nothing lasts forever.

Also -- you mentioned instructions; in case you need the manual, you can download it here:

I hope this helps, and please write back with any additional questions you have.

Best Regards,


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Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


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