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Daikin mini-split error H6: position sensor abnormality (compressor start-up failure)

By Jason Dearmin · Last reviewed November 14, 2026 · How we check facts

Short answerOn Daikin inverter wall-mounted heat pumps, H6 is a position sensor abnormality, which means the compressor failed to start in about 15 seconds after the run command. The code is listed in the FTXC, FTX-B, AXVJU and FTX-N/U service manuals. Daikin's service manuals list the causes as supply voltage problems, a disconnected compressor harness, a defective compressor or outdoor PCB, and a closed stop valve.
Brand check Many websites list H6 as a Mitsubishi code. We read official error and fault tables in 12 manufacturer documents covering Mitsubishi Electric MSZ/MUZ M-Series (GX, GL, FH and FS), MXZ multi-zone, P-Series PUZ/PUY, CITY MULTI, Ecodan, the PAR-40MAA remote, and Mitsubishi Heavy Industries SRK-ZS units. None of those tables lists H6 as an error code. (Ecodan documents use TH6 as the name of a thermistor, which is not a fault code.) The definition below comes from Daikin's service manuals. If you have a Mitsubishi unit, use the manual for your exact model. We have not checked every Mitsubishi document ever published, so we do not claim H6 is never used.

What H6 means

Daikin service manual DAMA-SM-23-020 (FTXC series) describes H6 as a position sensor abnormality. The unit detects it by checking the compressor running condition through the position detection circuit. The decision condition is that the compressor fails to start in about 15 seconds after the run command is sent; if the error repeats, the system is shut down.

Which Daikin manuals list H6

H6 appears in the error code table of every Daikin wall-mount service manual we read. The wording is nearly identical across them:

Daikin manualModelsH6 wordingDetection notes
DAMA-SM-23-020FTXC seriesPosition sensor abnormalityCompressor fails to start in about 15 seconds after the run command
DAMA-SM-23-006 (2023)FTX09-24BXVJU / RX-BXVJU (and FTK-B cooling only)Position sensor abnormalityCompressor fails to start in about 15 seconds; system shuts down if the error repeats; reset after about 11 minutes of continuous running
AXVJU service manual, section 3.3FTXB / FTXN 09-24 AXVJU with RXB / RXNPosition sensor abnormal (compressor)Listed for all four capacity classes (09, 12, 18, 24)
SiUS091601ED (03/2022)FTX-N/U wall, FVXS floor and FDMQ ducted units with RXL outdoor unitsPosition sensor abnormalityStart-up failure detected through the position detection circuit; system shuts down if it repeats; same 11-minute reset condition
SiUS091133 / SiUS04-924 (via easymanua.ls)RXS18LVJU, FTXS36HVJUPosition sensor abnormalityOlder FTXS / RXS service manuals with the same section title

All four current manuals list the same supposed causes: power supply voltage out of specification, a disconnected compressor harness, a defective compressor, a defective outdoor unit PCB, a start-up failure caused by a closed stop valve, and input voltage outside the specified range. A closed stop valve is mainly a new-installation problem; on a system that has run for years, the voltage and electrical causes are more relevant.

Reset condition

The manual lists the reset condition as continuous running for about 11 minutes without any other error. So a unit that recovers, runs, and then shows H6 again later is still reporting a start-up problem.

Daikin's list of supposed causes

The troubleshooting flow chart starts with turning off the power and checking that the supply voltage is as rated, then checks the discharge pressure (replace the stop valve if not OK) and the diode bridge. These steps need meters and refrigerant-side knowledge, so they belong to a technician.

What a homeowner can do

Electrical safety Do not open the outdoor unit or touch the compressor harness. The service manual itself warns to turn off the power switch before connecting or disconnecting connectors.

Safe homeowner checks for Daikin H6

  1. Check the breakerConfirm the outdoor unit breaker is on and has not tripped.
  2. Clear snow and ice around the outdoor unitGently remove snow or ice from the sides and top without touching internal parts.
  3. Restart onceTurn the system off at the remote, wait several minutes and restart once.
  4. Call for serviceIf H6 returns, record the model number and call a licensed technician.

Frequently asked questions

Does H6 mean the compressor is dead?

Not necessarily. The compressor is one of six causes in Daikin's list. Voltage problems, a loose harness, a closed stop valve or the outdoor PCB can also produce the same code.

Is H6 a Mitsubishi code?

We did not find H6 listed as an error code in the 12 official Mitsubishi Electric and Mitsubishi Heavy Industries documents we checked, which cover M-Series mini-splits, MXZ, P-Series, CITY MULTI, Ecodan and MHI SRK-ZS units. The H6 definition on this page comes from Daikin service manuals. Other Mitsubishi models can use different code sets, so check your own manual. We do not claim H6 is never used on a product we have not checked.

Sources

Related

/codes/daikin-mini-split//codes/mitsubishi-mini-split/Heat pump in defrost mode

Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.