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Carrier · Mini-split

P4 Compressor drive fault

High severity Carrier DLCM(R/H)B multi-zone outdoor

What the control is telling you

Compressor drive problem; same checks as the IPM fault. Shown on the 48K high heat model.

Applies to: DLCMHBH48EAK (48K high heat) only

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 supply is 208-230 V, 1 phase, 60 Hz and the power leads are tight.
  3. Measure DC across P and N on the IPM 277-356 V on 18-27K units, 277-410 V on 36-48K units.
  4. Check the cable between the main board and the IPM, the compressor leads, and every terminal in the electrical box.
  5. Check the bridge rectifier (no terminal pair should read 0 ohms) and each reactor lead for an open.
  6. Make sure the outdoor fan runs and the unit can breathe. If the fan is the problem, follow the fan fault (EC07).
  7. Check compressor winding resistance (should be equal on all three pairs).
  8. Replace in this order and retest each time: IPM module, outdoor main board, compressor.

Models that show this code

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

DLCMHBH24CAKDLCMHBH30DAKDLCMHBH36DAKDLCMHBH48EAKDLCMRBH18BAKDLCMRBH36DAKDLCMRBH48EAK

Other codes on the same units

  • P0 Inverter module (IPM) fault
  • P1 Over or under voltage protection
  • P2 Compressor top overheat (OLP)
  • P3 Low outdoor temperature cut-off in heating
  • P7 IPM temperature sensor fault
  • PC00 Inverter module (IPM) protection
  • PC0A Condenser high temperature protection
  • PC0F PFC module protection

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Source: DLCMRBH/DLCMHBH Multi-Zone Outdoor Service Manual (sold as Midea, Carrier and Viessmann Vitocal 200-S; Viessmann doc 6225551-03, 12/2024), Table 24 Outdoor Unit Error Display (48 High Heat only) p.27; diagnosis p.68. 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.