My house has a wired smoke alarm system, three smoke detectors and one CO detector. These are all old firex detectors, I am replacing them with three kiddie smoke alarms where one is combo CO + smoke detector.
The problem is if I remove the old CO detector and leave it disconnected the alarms chirp every 5-10 minutes. I put it back in and the chirping reduced to rarely a couple times a day.
How can I fix this setup to remove that old detector from the system?