HVACopediaViessmann · Mini-split
PC03 Pressure protection
What the control is telling you
High or low pressure switch tripped (see PC30 / PC31 on the outdoor unit).
Applies to: DLFSHBH high wall indoor units 09-24K (Midea / Carrier / Viessmann) on DLC multi-zone or single-zone outdoor units
Likely causes
- See PC30 / PC31
Test and repair steps
- Safety kill power at the disconnect and wait for the inverter capacitors to discharge before touching boards or wiring.
- Check the high-pressure switch wiring to the main board.
- Unplug the switch and measure it. A good switch reads 0 ohms at rest; open = replace it.
- If outdoor air is above 122 F (50 C), the unit is outside its range: shut it down.
- Check outdoor airflow nothing blocking the coil, coil clean, outdoor fan running (see EC07 if not).
- Check the refrigerant side (overcharge, restriction). If everything checks out, replace the outdoor main board.
Models that show this code
5 models in Viessmann DLFSHB high wall indoor
Other codes on the same units
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Source: Carrier MS-DLFSHB-01 High Wall Ductless Service Manual (04/2021), Table 9 p.17. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.