Dirty Filter Switch Trip alarm

What does Dirty Filter Switch Trip mean?

This alarm is activated when the dirty filter switch (DFS) closes, sending a 24 VAC signal to the SEC board. It indicates that the air filters need to be changed.

• Dirty or clogged air filters
• Blocked or incorrectly installed port tubes on the DFS switch
• High return static pressure
• Faulty DFS switch
• Faulty SEC board

Click steps to track your progress.

1. 1

   Check and clean or replace the air filters. If they are clean, proceed to the next steps.

2. 2

   Ensure the DFS switch's port tubes are correctly installed and not blocked.

3. 3

   Check for a 24 VAC input to the SEC board's DFS input, which should trigger the alarm if the switch is closed.

4. 4

   If the switch is closed and everything else is okay, check the return static pressure. If it exceeds 0.2 in. w.c., address the cause of high static pressure.

5. 5

   If the SEC board shows the alarm with no 24 VAC input and all other checks are clear, power cycle the unit. If the alarm persists, replace the SEC board.