Like some others have complained about I have had some issues with the filter alarm coming on when the filter was not plugged. As was mentioned by someone else I believe in this forum the problem is worse during cold weather when the humidity drops in my basement. Note, because of my gassification boiler the heat pump still has a lot of energy to work with.
Anyway, with recent cold weather it started to happen again. Last winter I found that if I left the filter off the alarms would stop so this year I took a closer look at it. I used a big screwdriver to pry the louvers open a bit more to straighten out the air flow through the filter and to better direct it toward the evaporator coil and the alarms have stopped. It has been about 2 weeks since I did this and no more alarms. As a fringe benefit there is a lot less noise from the air flow than there was before. Before I did this the noise would increase substantially when the filter was installed due to turbulence but now it makes no change.
Anyway, with recent cold weather it started to happen again. Last winter I found that if I left the filter off the alarms would stop so this year I took a closer look at it. I used a big screwdriver to pry the louvers open a bit more to straighten out the air flow through the filter and to better direct it toward the evaporator coil and the alarms have stopped. It has been about 2 weeks since I did this and no more alarms. As a fringe benefit there is a lot less noise from the air flow than there was before. Before I did this the noise would increase substantially when the filter was installed due to turbulence but now it makes no change.