Indoor unit displays E6 and will not run in cooling or heating; sometimes occurs after installation or service.

Safety: Turn off all power supplies to both indoor and outdoor units at the breaker before working on wiring.

Steps:

• Verify power: Confirm that the outdoor unit is receiving the correct supply voltage (per nameplate) and that breakers are not tripped.
• Check interconnect cable: Open the indoor and outdoor terminal covers and verify that the communication and power terminals (often labeled 1-2-3 or L-N-S) are wired identically at both ends.
• Tighten terminals: Ensure all screws are tight and that no copper is exposed outside the terminals. Look for signs of overheating or melted insulation.
• Inspect cable: Follow the cable run and check for physical damage, rodent chewing, or water ingress at junction boxes.
• Polarity and grounding: Make sure line and neutral are not reversed and that the system is properly grounded as per Westinghouse installation instructions.
• Reset system: After correcting any wiring issues, power both units off for 5–10 minutes, then restore power and attempt to start the system.
• PCB diagnosis: If wiring and power are correct but E6 persists, either the indoor or outdoor PCB communication circuit may be defective. Swapping boards or advanced diagnostics should be done by a professional.

Warning: Miswiring can damage control boards. If you are unsure about electrical wiring, hire a licensed electrician or HVAC technician.