E18
Johnson Controls
Ventilation Output or Feedback Fault
Thermostat shows E18 and cannot detect or control an external ventilation device (ERV/HRV or fresh air damper).
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Open circuit to ventilation relay, Miswired vent terminals, Failed ventilation relay on thermostat or controller, Incorrect configuration of ventilation type
How to Fix / Troubleshooting
Safety: Turn off power to HVAC and any connected ventilation equipment before working on wiring.
- Step 1 – Verify configuration: In the installer menu, confirm the correct ventilation device type (ERV/HRV, fresh air damper, etc.) is selected.
- Step 2 – Inspect wiring: Check the ventilation control terminals on the thermostat or Johnson Controls interface module. Ensure wires are secure and match the ventilation device terminals.
- Step 3 – Check device operation: Bypass the thermostat by manually energizing the ventilation device per its manual (e.g., test switch or jumper). If it does not run, the device itself may be faulty.
- Step 4 – Test output: With a ventilation call active, measure for the expected control signal (24 VAC or dry contact closure) at the thermostat’s ventilation output.
- Step 5 – Replace faulty component: Replace the ventilation relay/interface module or the thermostat main control board if it is not providing the correct output.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Ventilation Control Relay / Interface Module
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements