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Carrier · Mini-split

E1 Indoor / outdoor communication error

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

What the control is telling you

Same fault as EL01. 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. Cycle power at the breaker. If the code clears, watch it for a while.
  3. Check L1, L2, S and ground between outdoor and each indoor terminal block against the diagram. The S wire is polarity sensitive. Use 14/3 stranded with ground, never thermostat wire.
  4. With the unit on, put the red lead on terminal 2 (L2) and black on S (or terminal 3) at the outdoor unit. A healthy line swings back and forth between + and - DC. Stuck positive = outdoor board side. Stuck near zero = indoor side.
  5. Press the outdoor check button (SW1) once: the display shows how many indoor units are talking. Compare with the number installed.
  6. Check the IPM board LEDs and the main board LED are lit, and that the reactor wiring is tight.
  7. Swap parts in this order based on what you found: indoor PCB, IPM board, outdoor main PCB.
  8. In high EMF areas a 14/2 shielded cable can replace L2 and S, shield grounded at the outdoor unit only.

Models that show this code

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

DLCMHBH24CAKDLCMHBH30DAKDLCMHBH36DAKDLCMHBH48EAKDLCMRBH18BAKDLCMRBH36DAKDLCMRBH48EAK

Other codes on the same units

  • EC07 Outdoor fan speed out of range
  • EC50 Outdoor temperature sensor fault
  • EC51 Outdoor EEPROM error
  • EC52 Condenser coil sensor (T3) fault
  • EC53 Outdoor ambient sensor (T4) fault
  • EC54 Discharge temperature sensor (TP/T5) fault
  • EC55 IPM temperature sensor fault
  • EC56 Indoor coil outlet sensor (T2B) fault

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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.46-48. 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.