Condition
- Air proving switch failed to close
Possible Cause
- Check switch connections and wiring
- Blocked Vent
- Vent must always go uphill towards the termination
- Listen to vent outside if possible for water noises
- Blocked air inlet
- Blocked or disconnected air proving switch tube
- Remove tubing and blow through it
- Inspect for kinks
- Inspect for cracks/splitting in the tubing
- Blocked heat exchanger
- Blocked burner
