Drain Float Switch Connector Error

What it means

This code appears on the wired remote of Mitsubishi Electric Mr. Slim ducted, ceiling and cassette units. It means the indoor control board cannot see the drain float switch that monitors the water level in the drain pan, so it treats the switch as disconnected. The unit stops because it cannot confirm that water will not overflow into the ceiling. The same code can mean something else on other brands, and wall-mounted Mitsubishi Electric models show errors as lamp blinks with a different meaning.

Models covered: Mitsubishi Electric ducted, ceiling and cassette units (Mr. Slim) with check codes on the wired remote; wall-mounted Mitsubishi Electric models may show errors as lamp blinks with a different meaning.

Related codes: P5P6

Symptoms4

• The unit stops and P4 shows on the wired remote.
• The code appears after a new installation or after the unit was opened for service.
• The code returns immediately after restart because the connector is truly open.
• Usually no water leak, since the problem is the connection rather than the drain itself.

Possible causes5

• The float switch connector is unplugged or poorly seated on the board after service.
• The float switch lead is cut or pinched inside the unit.
• Corroded connector pins from moisture inside the concealed unit.
• A failed float switch.
• Wrong settings or a fault on the indoor control board (less common).

How to diagnose5

1. Switch off at the breaker for a few minutes and restart; if the code returns at once, an open connector is most likely.
2. Note whether the code appeared after the unit or drain pan was opened, which points straight to the connector.
3. With power off, the technician checks and reseats the float switch connector on the board.
4. The technician traces the lead to the switch and checks it for damage and continuity.
5. The technician confirms the code meaning and settings in the model's service manual, then checks the board if the code stays.

How to fix5

1. Reseat the float switch connector firmly on the control board.
2. Clean the connector pins or repair the damaged lead.
3. Replace the float switch if it has failed.
4. Replace the indoor control board if its circuit is at fault.
5. Pour a little water into the drain pan after the repair and confirm the drain pump runs and the code is gone.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is often just a technician visit and reseating the connector, and rises if the float switch or control board must be replaced.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions