CO Detector constant yellow

I tried to install my CO detector tonight, but when I removed the power tab the yellow "fault" lights up steady. I tried taking the batteries out and putting them back in, but same results.

Does this mean my CO detector is defective?


@ splogue Thanks for posting!

@ splogue

Thanks for posting! A constant yellow light on the CO Detector means that the sensor is not mounted on its bracket properly. Once mounted securely on the plate, the yellow light should go out. The mounting plate must be in place to relieve the tamper condition.

Ryan K.
SimpliSafe Home Security

I have the same issue. My

I have the same issue. My replacement CO detector is securely mounted to the plate, displays a steady yellow light and chirps once a minute. Beyond annoying.

@hbell A steady yellow light


A steady yellow light and chirping like that indicates that the smoke detector isn't mounted properly, or that something is stopping the black tamper switch from being pressed. I would suggest that you remove your smoke detector, try cleaning it to ensure nothing is trapped and stopping the switch from pressing, and remount it. If you still have trouble, please give us a call so that we can help further!

SimpliSafe Home Security

My issue with the CO Detector

My issue with the CO Detector is I get an intermitting chirp I thought was indicating the batteries are low. I also get a "not responding code" at the keypad indicating it's the one and only CO we have (yes, the serial numbers match up). So, I change the batteries, test it and all is well. I mount the CO back on the bracket properly ensuring it is seated properly and the Fault light goes off. All is well, right? Hours later, same thing; an intermitting chirp. Really? So, I think to myself, "could it be the "new" batteries were bad?" I go to the store, purchase new batteries, replace the batteries. Same thing. What is going on? Could this CO be deffective?

@info_444 Thanks for


Thanks for reaching out about this. It sounds like there may be a more persistent issue with the CO detector that would be best diagnosed over the phone with our support team. If you haven't already, give us a call at 1-800-548-9508 and our team will be happy to assist you in finding a fix.

SimpliSafe Home Security

I have recently been noticing

I have recently been noticing this same issue. I actually have noticed this occur in two different CO monitors from two different locations, and the most recent one is at home, and it is quite annoying. The first one, I just ended up unplugging, since it was at a location with low risk of CO poisoning and we couldn't figure out the issue. I will try calling the support team to see if they can diagnose, but I'm beginning to think this is a device quality issue.

What was the resolution to

What was the resolution to this? After 5 years, mine just started doing this in the middle of the night last night. I changed the batteries, thinking it was that, but to no avail.

Never mind, I found the

Never mind, I found the manual and the yellow light flashing four times is the "too old, replace" signal.

@halt00 Yeah, sounds like End


Yeah, sounds like End of Life signals from the CO detector.