Coleman air conditioner control shows E7 and the system may not respond to thermostat commands or may operate in the wrong mode.

Safety: Turn OFF power to the indoor unit at the breaker before removing thermostat or control board covers.

• Check thermostat power: Remove the thermostat from its base. Verify 24V between R and C with a multimeter. If no voltage, inspect the 24V transformer and low-voltage fuse on the Coleman control board.
• Inspect thermostat wiring: Ensure each conductor is firmly clamped in its terminal at both the thermostat and the air handler. Look for broken or shorted wires, especially where the cable passes through the wall or cabinet.
• Reset thermostat: Many Coleman-compatible thermostats have a reset function (check manual). Perform a factory reset and reprogram system type and settings.
• Check board connector: On some Coleman systems, the thermostat connects via a plug-in harness to the control board. Reseat this connector and inspect for bent pins.
• Substitute thermostat: If wiring and voltage are good, try a known-good compatible thermostat. If E7 clears, the original thermostat is defective.
• Board replacement: If a good thermostat still shows E7, the thermostat interface on the Coleman control board may be damaged and require replacement.

Note: Always match thermostat type (single-stage, two-stage, heat pump) to the Coleman system capabilities.