Blinking Display (four zeros) — Thermostat stuck in power-up sequence

What does Blinking Display (four zeros) mean?

The slave thermostat display shows four zeros that either blink on and off or are constantly displayed. This means the thermostat is repeatedly cycling through its power-up sequence and cannot enter normal operating mode.

• Low voltage from the 24 VAC transformer (outside 22 to 30 VAC range).
• Unsteady 10 VDC across the red and white wires from the damper actuator.
• A broken or disconnected yellow or blue wire from the damper actuator to the slave thermostat.
• Improperly installed or defective slave thermostat ribbon cable.
• Defective slave thermostat wiring connector board, slave thermostat, or damper actuator.

Click steps to track your progress.

1. 1

   Check the voltage from the 24 VAC transformer; it should be between 22 and 30 VAC.

2. 2

   Verify there is a steady 10 VDC across the red and white wires coming from the damper actuator.

3. 3

   Inspect the yellow and blue wires from the damper actuator to the slave thermostat wiring connector board for breaks or disconnections.

4. 4

   Ensure the slave thermostat ribbon cable is properly installed and not defective; disconnect and reseat it if necessary.

5. 5

   Refer to the 'Slave Thermostat Wiring' section on page 9 for further troubleshooting of the ribbon cable and wiring connector block.