Boiler shows E11, the burner will not start, and this may occur after thermostat wiring changes.

Safety: Turn off power before working on low-voltage wiring to avoid damaging the control board.

Steps:

• 1. Check thermostat: Ensure the thermostat is set to HEAT and the setpoint is above room temperature. Replace batteries, if applicable.
• 2. Inspect wiring at boiler: Remove the front panel and locate the thermostat or TT terminals on the control. Verify that wires are firmly attached and not broken.
• 3. Look for shorts: Inspect the thermostat cable along its path for crushed or exposed conductors. Repair or replace damaged cable.
• 4. Low-voltage fuse: Some Slant/Fin controls include a small fuse protecting the 24V circuit. Check and replace it with the same rating if blown, but only after correcting any short.

Professional help: If E11 persists with correct wiring and a known-good thermostat, the control board input may be defective and require replacement.