How to Troubleshoot a Nighthawk Carbon Monoxide Detector

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Exposure to carbon monoxide (CO) can cause severe illness or death. This noxious gas makes its way into homes with fuel-burning appliances, like gas stoves, dryers, and furnaces. Perhaps what's most insidious is that a CO leak can go undetected since the gas is colorless and odorless, leaving homeowners exposed and in potential danger.


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While you may not be able to identify whether there's CO around you, devices like the Kidde Nighthawk carbon monoxide detector constantly monitor for the presence of CO in your home and protect you from this stealthy threat. However, if you've noticed that something is off with your Kidde Nighthawk carbon monoxide alarm, perhaps an "Err" or "Lb" message, it's important to troubleshoot it immediately. A Kidde carbon monoxide alarm that fails to function properly puts you, your family, your roommates, and possibly your neighbors at risk of carbon monoxide exposure.


Troubleshoot a Kidde Nighthawk 'Lb' Message

If the display screen reads "Lb" along with an empty battery symbol, then there's good news: This is one of the simplest Kidde carbon monoxide alarm symptoms to treat. Your CO detector will also likely chirp every 30 seconds, accompanied by a flashing red light.


"Lb" stands for low battery. Your CO system is trying to let you know that you'll need to change the batteries and sooner rather than later. The Kidde Nighthawk carbon monoxide alarm does not monitor for CO while the "Lb" message is displayed.

Remove the front battery cover by gently sliding down the door. Take out the old batteries and replace them with three new AA batteries, following the polarity instructions. Replace the door. The display will show "888" for one minute before returning to normal operation.


Fixing an 'Err' Message

Unfortunately, an "Err" message on your Nighthawk CO detector's display doesn't go away with a simple battery change. This message could be the end of your entire unit. Before you throw out the Kidde carbon monoxide alarm, first try removing and reinstalling the batteries. Sometimes, the "Err" message shows if the batteries are incorrectly inserted into the device.


If the "Err" message continues to show or an "End" message appears, then it likely means that your CO detector has reached the end of its seven to 10-year life span. The unit will need a total replacement. Alternatively, "Err" could also mean a sensor malfunction. Either problem requires a brand-new CO detector.

Kidde will send a replacement CO system if your unit is under warranty when the "Err" message shows. Call customer service at 1–800–880–6788 to receive your replacement.


Solving for False CO Readings

Your Nighthawk carbon monoxide alarm shows a reading of CO levels in your home every 30 seconds on its digital display. However, certain substances can affect how well the sensor can detect CO, and these may cause a false reading of CO levels.

These substances can cause the detector to show an inaccurate amount of CO in your home:


  • Alcohol-based products.
  • Paints.
  • Thinners.
  • Solvents.
  • Adhesives.
  • Hair spray.
  • Aftershave/perfume.
  • Some cleaning agents.

If you're working on a home renovation that makes the use of some of these products unavoidable, simply remove your CO monitor for the duration of the project. Of course, it's paramount to replace the Kidde Nighthawk carbon monoxide alarm once your project is complete so your home isn't vulnerable to a CO leak.


Kidde Nighthawk Continuous Alarm Squeal

Sometimes, your CO alarm will try to get your attention for a reason other than CO levels. A CO alarm that continuously sounds, even when no dangerous CO is present, can seem like more of a nuisance than a benefit to your home, but it's annoying by design in order to get your undivided and quick attention.


A Nighthawk CO detector that sounds the alarm when no CO is present could have one of two conditions. The first is that the tamper-resistant feature has been triggered. All this requires you to do is to make sure your detector has not come unplugged or has loosened from the outlet.

An ongoing squealing CO alarm is also the fatal sound of a malfunction, and your unit will need to be replaced.



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