Indoor and Outdoor Unit Abnormal Communication

What it means

This code appears on Panasonic inverter split air conditioners when the fault history is read with the CHECK button on the remote. It means the indoor circuit board is not getting a valid signal from the outdoor board, so the compressor stops and the indoor fan may keep blowing without cooling. The same number can mean something else on other brands.

Models covered: Panasonic residential inverter split air conditioners (wall mounted); the code is read with the CHECK button on the remote control.

Related codes: H33H16F90F99

Symptoms4

• The indoor unit runs but the air is not cold.
• The outdoor unit does not start at all or stops after a few minutes.
• The timer or power lamp blinks on the indoor unit.
• The fault returns right after a restart or after a short time.

Possible causes6

• Loose or corroded wires at the terminal blocks of the interconnecting cable.
• No power reaching the outdoor unit because of a tripped breaker or a blown fuse on its board.
• A damaged interconnecting cable from heat, rodents or building work.
• Wires connected to the wrong terminals after installation or service.
• A faulty outdoor inverter board, often after voltage swings or overheating.
• A faulty indoor board (less common).

How to diagnose5

1. Switch the unit off at the breaker for a few minutes, restart it and see whether the code returns.
2. Make sure any separate outdoor breaker is on and that the supply voltage is stable.
3. With power off, the technician checks the cable terminals in both units and confirms the wiring order against the manufacturer diagram.
4. The technician checks that supply and signal reach the outdoor unit and compares them with the manufacturer specification.
5. The technician checks the outdoor board fuse and any diagnostic LEDs to decide which board is at fault.

How to fix5

1. Restart the unit after a power-off; the code may clear if a brief voltage dip caused it.
2. Tighten and clean the cable terminals and correct any wrong wiring.
3. Replace the interconnecting cable if it is cracked or cut.
4. Fit a voltage protector if the building supply is unstable.
5. Repair or replace the faulty board, then run the unit and have the technician confirm the code does not return in the fault history.

Repair cost

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

The cost stays low when a loose terminal or damaged cable is to blame, and rises sharply when the outdoor inverter board has to 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