Code: E6🔧 Cooper and Hunter Mini Split

Cooper and Hunter Error Code E6: Indoor and Outdoor Units Not Communicating (Meaning, Causes, Fixes)

Reviewed 2026-10-25 · Based on 4 manufacturer & service sources

What the code means

Cooper and Hunter's support knowledge base defines E6 as a communication error between the outdoor and indoor units. Its duct-type split service manual lists E6 as "Communication error": if the indoor board gets no signal from the outdoor unit, the compressor and outdoor fan stop, and the indoor fan and auxiliary heater stop too, so the machine won't run. The Cooper and Hunter Commercial Series service manual adds that E6 is reported when there has been no communication between the outdoor and indoor units, or between the indoor unit and the wired controller, for 120 seconds in a row. Cooper and Hunter's US support pages for Mia mini splits also carry an E6 Error Code Mini Split guide. Note that on some non-mini-split Cooper and Hunter products, such as energy recovery ventilators, E6 means something else, so check the code table for your model.

Likely causes

Safe DIY checks

⚠ Before you start

Mini split communication wiring often shares a cable with high-voltage power, and outdoor inverter boards hold a charge after power is cut. Switch off the breaker before touching the terminal blocks, and leave board testing and replacement to a licensed HVAC technician.

  1. Turn off the breaker or disconnect for the system, wait a few minutes and turn it back on to see whether the code clears.
  2. Look over the cable that runs between the indoor and outdoor units for cuts, crushing, chewing damage or splices.
  3. If you're comfortable working with power off at the breaker, check that each wire at the indoor and outdoor terminal blocks is tight and matches the numbered terminals on the wiring diagram. A swapped wire is common on new installs.
  4. If the wiring looks right and E6 keeps coming back, call an HVAC technician to check voltage and the control boards.

🛠 When to call a pro

  • Measure the supply voltage at the outdoor unit and confirm it's stable and in range (Cooper and Hunter's first check).
  • Check the interconnecting cable for continuity, correct terminal order at both ends and good contact, and confirm the plug and socket orientation of internal communication connectors.
  • Make sure any magnetic (ferrite) rings called for on the communication cable are installed at both ends, per the duct-type service manual's E6 flowchart.
  • Inspect internal wiring and connectors in both electrical boxes. On wired-controller systems, check the controller count and address settings.
  • If wiring and voltage check out, replace the outdoor control board or the indoor control board, as Cooper and Hunter's E6 article directs.

Parts that commonly fix it

Always match the part number to your exact model.

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Digital multimeter

For checking supply voltage and continuity of the interconnecting cable.

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Non-contact voltage tester

To confirm the power is off before opening the terminal covers.

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Indoor or outdoor control board

Only after the wiring and voltage check out. Match the part to your Cooper and Hunter model number.

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Sources

  1. Cooper and Hunter support knowledge base: E6, communication error between outdoor and indoor units (causes: unstable voltage, damaged cable, poor contacts, outdoor or indoor board; fixes in the same order)
  2. Cooper and Hunter duct-type split air conditioner service manual: trouble table E6 communication error and 2.5 E6 troubleshooting flowchart (cable connection, plug direction, magnetic rings)
  3. Cooper and Hunter Commercial Series R410A service manual: 3.4.5 E6 communication error, no communication for 120 s, possible causes
  4. Cooper and Hunter USA support: Mia mini split (CH-NY12MIA-115VO) manuals and E6 Error Code Mini Split guide

Last reviewed 2026-10-25. Always confirm against the manual for your exact model number.