RS‑485 Wiring Error Causing E6/P6 Communication Fault – Controller Goes Blank After Start‑Up

(New Install where unit worked for a short period– Incorrect RS‑485 Comms Wiring)

Applies to:
Braemar Dominator, SDHV 1‑phase ducted, KDHV, SACV, KACV and other Invertair systems using RS‑485 communication.

Controller Goes Blank / E6 or P6 Fault – New Installation

(Incorrect RS‑485 Comms Wiring)

1. What’s Happening?

A new system starts normally, but after a short time:

  • The controller screen goes blank,
  • The system won’t turn back on,
  • The outdoor unit or MagIQtouch shows E6 or P6 communication faults.

Both the indoor and outdoor units still have power.

2. What’s the Actual Problem?

The communication wires (comms) have been connected to the wrong terminals inside the indoor unit.

These systems use two separate communication connections:

TerminalsWhat They Are For
1 / 2Outdoor unit communication
H1 / H2Wired wall controller (NOT used on AOC)

Important Note for Invertair Add‑On Cooling (AOC):

For AOC systems (SACV / KACV), H1/H2 are meant to be left empty.
MagIQtouch/ICS control does not connect to these terminals — it connects using the Modbus communication loom plugged directly into the indoor PCB.

So, if the installer mistakenly wires the controller into h1/h2 or accidentally swaps any comms pair with 1/2, the system will lose communication once it goes into standby mode.
This is what causes the controller to go blank and the E6/P6 errors to appear.

No PCB is faulty — it’s a wiring mix‑up.

3. What Do E6 and P6 Mean?

Very simply:

E6 – “I’ve lost communication”

The indoor and outdoor can’t talk.
Usually caused by swapped wires, loose wires, or polarity reversed.

P6 – “I’ve been losing communication for a while”

The outdoor unit gives up and shuts the system down for safety.

Both clear automatically once the wiring is corrected.

4. How to Fix It

  1. Turn all power off to indoor and outdoor units.
  2. Check the indoor PCB wiring:
    • Outdoor communication → must go to 1/2
    • H1/H2 → must stay EMPTY for AOC systems
    • MagIQtouch/ICS → must use the Modbus loom, not H1/H2
  3. Correct any wiring mix‑ups.
  4. Tighten terminals properly.
  5. Turn power back on.
  6. Controller should stay on, and the fault codes will disappear.

5. How to Avoid This Issue

  • Always check the wiring diagram — don’t wire based on colour alone.
  • For AOC, remember: do not use h1/h2.
  • If a new unit works once then dies shortly after → suspect swapped comms first, not a failed PCB.