Troubleshooting My Philips Avent bath thermometer does not show readings. The Philips Avent bath thermometer is here to make your life easier. If it does not show readings it might be time to replace the battery. Step-by-step instructions Push firmly to remove the measurement unit from the rubber housing (Fig.1)Ensure that there are no water droplets on the measurement unit, dry it with a paper towelRemove the 4 screws with a small screwdriver and remove the battery housing cover (Fig.2)Carefully remove the empty batteries and insert new batteries (two LR44 coin batteries).Screw the screws back in the battery housing to close it again.Push the measurement unit back into the rubber housing. Note: only use the recommended batteries and make sure that you have properly assembled the device before use.