Mitsubishi: Condensate Drain / Float Switch Fault

What this fault means

A wall-mounted or ducted indoor unit tripped its drain protection because condensate is not clearing — a P5-type drain fault on Mitsubishi units.

Likely causes

• Blocked condensate drain line
• Failed drain pump (on units that use one)
• Float switch fault
• Improper drain slope

What you can safely check

• Replace a dirty air filter — restricted airflow causes a surprising share of furnace faults.
• Confirm registers and the outdoor unit are clear of snow, leaves and debris.
• Cycle power at the switch once and let the system retry.

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