Code: PB🔧 Mitsubishi Mini Split

Mitsubishi Mini Split Error Code PB: Indoor Fan Motor Error (Meaning, Causes, Fixes)

Reviewed 2026-10-24 · Based on 3 manufacturer & service sources

What the code means

Mitsubishi Electric's service manual for the PKA-A12HA7/PKA-A18HA7 wall-mounted indoor units (OCH637) lists PB (Pb) as "Indoor fan motor error" in its self-diagnosis table, shown on an IR wireless remote setup as 11 beeps or 11 blinks of the OPERATION INDICATOR lamp. Its troubleshooting table names this check code "Fan motor trouble" and gives two causes: a defective fan motor and a defective indoor controller board, with the instruction to follow the DC fan motor check (fan motor/indoor controller circuit board). Mitsubishi Electric Singapore's Mr. Slim error chart uses the same 11-blink pattern and calls it "Indoor unit fan motor error." The outdoor unit service manual for PUZ-A/PUY-A NKA7 and NHA7 units (OCH636E) also lists Pb as "Indoor fan motor trouble" with the outdoor board indicator blinking 5 times, and says to check the winding of the indoor unit fan motor, referring to the indoor unit service manual for details.

Likely causes

Safe DIY checks

⚠ Before you start

Unplug the appliance or switch off its breaker before opening panels.

  1. Write down the code and count the beeps or blinks; PB is 11 on Mitsubishi's wireless-remote table.
  2. Turn the system off and look into the air outlet. If something is jammed in the fan wheel (the long barrel-shaped fan in a wall unit), that's worth telling the technician; don't reach into the unit while it has power.
  3. Clean the indoor air filters and make sure the intake and outlet aren't blocked.
  4. Turn the system off at the breaker for a few minutes and restart it. If PB comes back, stop resetting it and call an HVAC technician.
  5. Don't unplug or test the fan motor connector yourself. Mitsubishi warns that high voltage (around 300 V DC) is on that connector and that pulling it with the power on can damage both the board and the motor.

🛠 When to call a pro

  • Confirm the code with the remote's self-diagnosis or at the outdoor controller board (Pb shows as 5 blinks in the OCH636E outdoor table).
  • With the power off, check the contact at the fan motor connector (CNMF) on the indoor controller board and repair any wiring fault.
  • Power supply check with CNMF removed: on the indoor controller board, measure between pins 1 (+) and 3 (-) for about 294 to 325 V DC, and between pins 4 (+) and 3 (-) for 15 V DC. If either is wrong, check the board fuse; replace the fuse if it's blown, otherwise replace the indoor controller board.
  • If the power supply is normal, run the fan and measure the sensor signal between CNMF pins 6 and 3. If it doesn't repeat between 0 and 15 V DC, replace the fan motor; if it does, replace the indoor controller board.
  • After each part change, check the fan's operation before closing up. On OCH636E outdoor units Mitsubishi also says to check the winding of the indoor fan motor.
  • Use the exact motor and board part numbers from the indoor unit's service manual. Under warranty, go through the installing contractor or a Mitsubishi Electric Diamond Contractor.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Mini split indoor fan motor (exact part for your indoor model)

Mitsubishi lists a defective fan motor as the first PB cause; match the part number to your indoor unit's service manual.

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⚙

Mini split indoor controller board (exact part for your indoor model)

The other PB cause is a defective indoor controller board; check the board fuse first.

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⚙

Digital multimeter

Used for Mitsubishi's CNMF voltage checks (about 300 V DC and 15 V DC); the high-voltage test is for trained technicians.

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Sources

  1. Mitsubishi Electric PKA-A12HA7/PKA-A18HA7 indoor unit service manual OCH637: self-diagnosis table (PB/Pb indoor fan motor error = 11 blinks/beeps), troubleshooting table (fan motor trouble: defective fan motor or indoor controller board) and section 9-6-2 DC fan motor check (CNMF contact, 294-325 V DC and 15 V DC test points, fuse, 0/15 V sensor signal), via Mitsubishi Tech Info Canada
  2. Mitsubishi Electric outdoor unit service manual OCH636E (PUZ-A/PUY-A12-42 NKA7/NHA7): Pb indoor fan motor trouble, outdoor indicator 5 blinks, check the winding of the indoor unit fan motor, via Mitsubishi Tech Info Canada
  3. Mitsubishi Electric Singapore Mr. Slim error code chart (PB(Pb) indoor unit fan motor error, 11 blinks)

Last reviewed 2026-10-24. Always confirm against the manual for your exact model number.