Thermostat displays E15 and may not control ventilation; fresh air intake or ERV/HRV does not operate as expected.

Safety first: Turn off power to the ERV/HRV and HVAC system at the breaker.

• Step 1 – Verify ventilation settings: In the thermostat's advanced menu, ensure ventilation is enabled only if an ERV/HRV or fresh air damper is installed.
• Step 2 – Inspect VENT wiring: At the thermostat and ERV/HRV, check that the VENT control wires are secure and correctly landed per Carrier's wiring diagram.
• Step 3 – Check ERV/HRV unit: Open the ERV/HRV access panel and inspect for blocked filters, seized fan, or ice buildup. Clean or replace filters and ensure the fan spins freely.
• Step 4 – Test operation: With power restored and a manual call for ventilation from the thermostat, listen for the ERV/HRV fan. If it does not run and there is control voltage present, the internal control module or motor may be failed.
• Step 5 – Replace failed module: Replace the Carrier ERV/HRV control board or motor assembly as required.
• When to call a pro: Ventilation systems affect indoor air quality and pressure balance; a Carrier technician should verify proper operation after repairs.