What this code means
Mitsubishi error code P5 indicates a drain pump fault. The control board commanded the condensate pump but did not see the expected water-level response. This code is common on cassette, ceiling-concealed, and some ducted Mitsubishi indoor units that use a lift pump.
Common Causes
- Failed drain pump motor — The pump winding is open or the motor is seized.
- Pump impeller jammed — Slime or debris has locked the impeller.
- Float switch not resetting — The pan switch still reports high water even after pumping.
- Blocked discharge tube — The pump runs but water can’t leave the unit.
Step-by-Step Fix
- Turn off power to the indoor unit.
- Access the drain pump assembly and inspect for standing water.
- Disconnect the discharge tube and verify it is open.
- Remove the pump and inspect the impeller for slime or debris buildup.
- Test the pump winding with a multimeter for continuity.
- Replace the pump if the winding is open or the motor hums without moving water.
- Verify the float switch resets once the pan is empty.
Parts Often Needed
| Part | Notes |
|---|---|
| Drain pump assembly | Amazon | Model-specific Mitsubishi part |
| Float switch | View on Amazon | Often sold separately |
| Discharge tubing | Amazon | Replace if kinked or brittle |
When to Call a Pro
If the pump receives power but still doesn’t run, or if the fault involves concealed piping in a ceiling, call a Mitsubishi-trained service tech to avoid water damage.