PC30 High pressure protection

What the control is telling you

The high-pressure switch opened. Outdoor board shows P1; 48K HH shows J5.

Applies to: DLCMRBH / DLCMHBH multi-zone outdoor units 18-48K (Midea, Carrier, Viessmann Vitocal 200-S)

Likely causes

• Loose switch wiring
• Bad switch
• High outdoor temperature
• Poor outdoor airflow / dirty coil
• Overcharge or restriction
• Bad outdoor PCB

Test and repair steps

1. Safety kill power at the disconnect and wait for the inverter capacitors to discharge before touching boards or wiring.
2. Check the high-pressure switch wiring to the main board.
3. Unplug the switch and measure it. A good switch reads 0 ohms at rest; open = replace it.
4. If outdoor air is above 122 F (50 C), the unit is outside its range: shut it down.
5. Check outdoor airflow nothing blocking the coil, coil clean, outdoor fan running (see EC07 if not).
6. Check the refrigerant side (overcharge, restriction). If everything checks out, replace the outdoor main board.

Models that show this code

7 models in Carrier DLCM(R/H)B multi-zone outdoor

Other codes on the same units

• PC06 Discharge temperature protection
• PC08 Outdoor over-current protection
• PC10 Low AC supply voltage
• PC11 AC supply voltage protection (over voltage)
• PC12 DC bus high voltage / 341 MCE error
• PC31 Low pressure protection
• PC40 Main chip to compressor drive chip communication error
• PC42 Compressor start failure