Display shows E009; unit may not respond to thermostat or demand signal.

Safety: Turn off power before working on low-voltage control wiring.

Steps:

• 1. Verify wiring: Compare the thermostat or external call-for-heat wiring to the Lochinvar wiring diagram. Ensure wires are landed on the correct terminals and polarity is observed where required.
• 2. Check for shorts: Inspect the thermostat cable for staples through the jacket, crushed sections, or exposed copper. Repair or replace damaged cable.
• 3. Test thermostat: Disconnect the thermostat wires at the heater and temporarily jumper the call-for-heat terminals. If the unit operates normally with the jumper, the thermostat or external controller is suspect.
• 4. Measure control voltage: Use a multimeter to verify the correct control voltage (often 24V) is present at the thermostat terminals when expected.
• 5. If E009 remains: The control board's input circuit may be faulty and require replacement.