Heil communicating thermostat shows E5; outdoor unit does not respond to cooling calls

Safety first: Turn off power at the outdoor disconnect and indoor breaker. Use a multimeter only if you are comfortable and trained to do so.

• Step 1 – Check outdoor disconnect: Verify the pull-out or breaker at the Heil condenser is fully inserted and not tripped. Reset if necessary.
• Step 2 – Inspect indoor 3–5A low-voltage fuse: On the indoor control board, locate the small automotive-style fuse. If blown, replace with the same rating. If it blows again, there is a short in the thermostat or outdoor wiring.
• Step 3 – Inspect thermostat cable: Look for damaged insulation, staples through the cable, or corrosion at wire nuts and terminals between indoor and outdoor units.
• Step 4 – Check outdoor board LEDs: With power restored, observe the outdoor control board status LED. No lights usually indicate no power or a failed board. Refer to the Heil service label for LED code meanings.
• Step 5 – Replace outdoor board if needed: If correct power and wiring are present but the board is unresponsive, replacement of the outdoor control board is typically required by a technician.