I just installed the new 200 gal filter cartridge I bought, and just as has happened each time before, the darn meter didn't come back on. I saw lots of users also have this problem. Some didn't seem to get help from Dupont customer services. I did. So I'm sharing the instructions I was sent by their customer service dept. the last time (2018) I ran into a problem with the meter not engaging when I replaced the filter, & some tips I've found helped me. >>>>>>>>>>>>>>>>>>> Instructions on how to straighten the cartridge sensor on the FM350 water filter Meter often quits after inserting new or changing filter. Prong at end of filter tends to disable sensor in reader. You may have to repeat these steps 2 – 3 times for sensor to go back in place. Please follow instructions below on how to reset the cartridge sensor on the FM350 water filter Remove the cartridge from the back. Unscrew the meter from the front. On the back of that you should see a small, black button. This is the cartridge sensor. If the sensor is bent or crooked, take your thumb and straighten it out as best you can. Put the meter back on to the front, turn it until you hear a click, and re-insert the cartridge. Be sure to support it from the bottom so that you do not break it off at the mounting nut. When you do this the display should flash blue and read ---. Turn the water on and then the filter. When you do this the display should read “FLH” for the flush cycle. Light will come on for a few minutes and then it will go out in order to save the battery life, but meter will continue working. Let the flush cycle run. It should not take longer than 5 to 6 minutes. After that the counter should reset itself to read 000. If this does not work, please contact me at 1-866-709-2086 ext. 2113 and we will go from there. You can continue to use this unit until we can get the situation resolved. Once you do the first initial 5 minute flush of the cartridge the water is going to be filtered regardless of what the meter does. Again, I apologize for any inconvenience that this has caused you. If I can be of any further assistance, please let me know. >>>>>>>>>>>>>>>>>>>>>>> Note: I haven't tried the ph.# above, so don't know if it's current. Some tips: Both the filter cover and the meter cover are quite tricky to get back in place exactly right. The meter won't work if you haven't got the filter in absolutely properly, and the cover screwed completely straight and tight. Sometimes that's the sole reason the meter doesn't seem to be working. So before fiddling with the meter cover and sensor, double, triple check you got the cartridge in properly and the cover absolutely perfectly screwed back on. It helps to clean any hard water deposits off before reassembling with the new cartridge in place. Ditto if you do remove the sensor/meter cover. And ditto for dealing with spraying or dripping water from the connection to the faucet water. Basically all the screw in/on designs are a major pain. Getting them exactly right is possible, but it can take patience, patience, patience... doing it slowly, carefully, sometimes several times over. I really, really like having an actual # gallons used meter, not some vague # hours used that other systems offer. The amount of water that runs out in an hour depends on the life of the filter, and water pressure, and how far open you've got the faucet. So why use # hours as a metric for quantity used?? IMO, kudos for Dupont for using a common sense and actually useful metering system. But, NOT for the other aspects of their design. I don't know if there are ways to design the screw on parts so the are more user-friendly, but if there are, doing that seems a total no-brainer from the perspective of wanting to develop brand loyalty in customers! Or put differently: why on earth not correct a design that is pretty much guaranteed to drive users crazy - and away from sticking with your product??
