Mitsubishi Air Conditioner Error P4

⚡ Quick Answer: The Mitsubishi Air Conditioner error code P4 indicates a communication failure between the indoor and outdoor units, typically caused by a malfunction... ✅ DIY Fixable

What Does Error P4 Mean?

The Mitsubishi Air Conditioner error code P4 indicates a communication failure between the indoor and outdoor units, typically caused by a malfunctioning drain sensor or wiring issue. This error may lead to the unit ceasing operation to prevent damage, often accompanied by blinking lights or indications of drainage problems. Regular maintenance of the drain system and prompt attention to this error can help ensure optimal performance.

Common Symptoms:

  • Error code P4 displayed on remote or unit panel
  • Unit may stop operation to protect system
  • Possible water drainage issues/overflow indications

Possible Causes

  • Drain sensor (float switch/thermistor) malfunction or abnormal reading (medium)
  • Poor connection or wiring issue related to the drain sensor (medium)

How to Fix Error P4

DIY Fix Check basic drainage and reset

  1. Turn off the unit using the remote or main switch
  2. Inspect visible drain pan and drain hose for blockages or standing water
  3. After clearing obvious blockages, restore power and attempt restart

Technician Only Inspect and repair drain sensor and related wiring

  1. Disconnect power to the unit completely
  2. Access the indoor unit drain area and locate the drain float switch/thermistor
  3. Check connector seating and wiring integrity to the control board
  4. Measure sensor resistance against expected normal values
  5. Replace faulty sensor or repair wiring as needed
  6. Test operation after repairs

Parts needed: Drain float switch/thermistor, Wiring harness/connectors

🛑 When to Call a Pro:
  • If error persists after basic drainage check and reset
  • If you are unfamiliar with safe access to internal components or wiring
  • If sensor wiring appears damaged and requires professional diagnosis

Technical Specifications

wattage N/A
component Control Board
resistance N/A
part_number Mitsubishi 9320A123
voltage_rating 220V AC

Common Questions

What does P4 error mean on Mitsubishi Air Conditioner?

The P4 error indicates a communication failure between indoor and outdoor units, often due to a drain sensor malfunction.

Can I fix Mitsubishi Air Conditioner P4 error myself?

Yes, you can perform basic checks on the drainage system and reset the unit to see if the error resolves.

How much does it cost to fix P4 error?

Repair costs for the P4 error typically range from $50 to $200+, depending on parts and labor in your region.

When should I call a technician for P4?

Call a technician if the error persists after basic checks, if you're unsure about accessing internal components, or if wiring appears damaged.

Sources & References

Data last verified: 2026-07-01

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