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E6: Communication Failure Within the System.

E6 TROUBLESHOOTING STEPS:

NOTES

  • If the E6 is displayed at power up then it is most likely an INDOOR unit issue.

  • If the E6 appears after 3 - 4 minutes then it is most likely an OUTDOOR unit issue.

  • E6 error codes will not reset until the problem is resolved.

  • Cool or Heat mode does not affect troubleshooting steps.

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SAFETY NOTE: Use caution and remove the main power from the system when connecting or disconnecting any wires or plugs.

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STEP 1: Verify the following

  • Color code of the 1, 2, 3, and Ground connections at indoor & outdoor units match.

  • Interconnecting cable is 14/4 600V stranded copper wire.

  • Properly connected earth ground from the outdoor unit to the electric panel.

  • Ensure solderless crimp connections are crimped correctly.

  • Check that the communication wire is not broken or spliced between indoor and outdoor units.

TIPS:

  • Interconnecting cable should have voltage and gauge rating on the outer casing.

  • Take pictures of the indoor and outdoor wiring to verify connections.

  • Write down on a notepad to confirm the connections.

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STEP 2: Condensate pump or indoor service disconnect

  • With power off, verify condensate float breaks Terminal 3 to the indoor unit and make sure the float is closed.

  • Indoor service disconnect should be 3 pole.

  • Ensure the color code is correct through the disconnect.

  • Double-check for aftermarket accessories wired into the system (e.g., condensate pump, door switch, smoke detector, wet switch).

TIPS:

  • Condensate pumps might be behind the indoor wall mount with different-colored wires at the indoor unit terminal.

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STEP 3: Keep all wires connected – measure & record voltage on a notepad

  • For a 230V unit:

    • N1 and 2 should read 0VDC-55VDC (fluctuating).

    • N1 and 3 should be 208/230VAC.

    • 2 and 3 should be 208/230VAC.

    • N1 and G should be 115VAC.

    • 2 and G should be 0-55VDC (fluctuating).

    • 3 and G should be 115VAC.

  • For a 115V unit:

    • N1 to 2 should be 0VDC - 55VDC (fluctuating).

    • N1 and 3 should be 115VAC.

    • N1 and G should be 0VAC.

    • 2 and G should be 0VDC-55VDC (fluctuating).

    • 3 and G should be 115VAC.

TIPS:

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STEP 4: Measure and record voltage at outdoor & indoor Unit (208/230V or 115V Unit)

  • Outdoor Unit:

    • Remove #2 wire.

    • N1 to 2 should read 54 to 56 VDC.

    • 2 to G should read 54 to 56 VDC.

    • Reconnect #2 wire and move inside.

  • Indoor Unit:

    • Remove #2 wire from Terminal 2.

    • N1 and 2 wire should be 54 to 56 VDC.

    • 2 Wire and G should be 54 to 56 VDC.

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STEP 5: Check Ohm Interconnecting cable between indoor and outdoor unit

  • Turn off Main Power or Disconnect.

  • Remove wires 1, 2, 3, and G at indoor and outdoor units.

  • Ensure wires are separated and not touching metal.

  • Confirm there is no measurable resistance between any of the wires.

  • Tie all 4 wires together inside and recheck ohms resistance reading between outdoor unit wires - should be close to zero between all wires.

TIPS:

  • Ohm testing interconnecting wire may not always verify cable integrity under high voltage.

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IF WRONG WIRE TYPE / WIRE SPLICED, OR UNIT IS NOT PROPERLY GROUNDED...

  • Replace Wire / Properly ground unit

TIPS:

  • Consider running a temporary interconnecting wire to test if it resolves the E6 error code.

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IF CONDENSATE PUMP OR INDOOR SERVICE DISCONNECT ARE WIRED INCORRECTLY OR A/C VOLTAGE IS INCORRECT

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OUTDOOR UNIT: IF THE 54 TO 56VDC IS NOT PRESENT, IS BELOW 50VDC OR IS FLUCTUATING FROM N1 TO 2, WITH THE WIRE OFF #2 TERMINAL

  • Verify line voltage at the board, check fuses on the filter board, and/or main board for open circuits.

  • If fuses are closed circuit, power off and disconnect all DC components plugged into the board and recheck for the 54 to 56VDC.

  • If voltage is proper, a component could be the issue. Use an ohm meter to find a shorted or grounded component.

  • If voltage is still not proper, replacing the main board may solve the issue.

TIPS:

  • A grounded or shorted compressor, fan motor, EEV, or thermistors can cause an E6 error code.

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INDOOR UNIT: WITH THE 2-WIRE DISCONNECTED INSIDE AND CONNECTED OUTSIDE AND THE VOLTAGE IS HIGHER THAN 56VDC FROM N1 TO THE 2-WIRE INSIDE

  • The interconnecting cable from inside to outside is faulty

TIPS:

  • Try a temporary interconnecting wire to see if it resolves the E6 error code / Verify the interconnecting cable is 14/4 600V stranded copper wire.

INDOOR UNIT: WITH THE 2-WIRE DISCONNECTED INSIDE AND CONNECTED OUTSIDE AND THE VOLTAGE IS HIGHER THAN 56VDC FROM N1 TO THE 2-WIRE INSIDE

  • Verify the indoor fan runs.

  • Switch mode to fan and turn on the fan. If the fan does not run, unplug it from the board and see if E6 is replaced with a new code for the indoor fan. If so, the fan motor may be faulty.

  • Ohm thermistors and check the display board if ok and the fan does run, then the indoor main board may be faulty.

TIPS:

  • A grounded or shorted fan motor, display board, or thermistors can drag down the communication bus voltage and cause an E6 error code.

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