Bosch Greentherm and Greenstar units use direct spark ignition. When the igniter fails, the unit throws Code A1.
Confirm igniter failure
- Turn off gas
- Trigger an ignition attempt
- In a dark room, look through the sight glass
- You should see a bright blue spark
- No spark = igniter or igniter cable
Replacement (DIY)
- Power off and shut off gas
- Remove front cover
- Locate igniter
- Disconnect cable from PCB; unscrew igniter
- Install new igniter; reconnect cable
- Restore gas, power on, test
Cost
OEM Bosch igniter: $50-100. OEM-equivalent: $20-60 (voids warranty during warranty period).
Bottom line
Visual confirmation before ordering. Replacement is straightforward DIY.