Ducted unit overflow traced to stuck condensate pump float, not pump failure

What we found

Ducted unit overflow can come from the drain pan, the drain line, or the pump system. The pump needs to be tested as a system. Motor function alone does not confirm the float switch is working.

• Pump motor ran when triggered manually with the test button.
• Float switch did not move freely through its full travel range.
• Sludge buildup was visible around the float mechanism inside the reservoir.
• Drain pan and drain line were clear of blockage.

Sludge had accumulated around the float switch inside the pump reservoir. The float was stuck in the down position and could not rise with the water level to activate the pump. Condensate filled the pan and overflowed onto the ceiling below.

What we did

The pump motor is working. The problem is the float switch, which is stuck from sludge buildup. Cleaning the float mechanism and reservoir restores normal pump activation. No pump replacement is needed, and the ceiling does not need to be opened beyond the existing access panel.

After the float mechanism was cleaned and its travel restored, the pump activated consistently at the correct water level. The overflow stopped and no ceiling work was required.

What we learned

Why pump overflow does not always mean pump failure.

• A condensate pump has two key components: the motor that moves water, and the float switch that triggers it. The motor can be perfectly healthy while the float fails to send the activation signal.
• Cleaning the float mechanism and reservoir restores normal switching behavior without replacing the pump assembly.
• Sludge and biofilm accumulate in the pump reservoir over time, restricting float travel. The float stays down and the pump never receives the signal to activate. It works fine when tested manually — the issue is the float, not the motor.