Digital Bunn coffee maker will not heat; display shows E01 shortly after power-up and brew will not start.

Safety first: Unplug the coffee maker and allow at least 30–45 minutes for the internal hot water tank to cool before opening any panels. Hot water and metal surfaces can cause burns.

Steps to check:

• 1. Power reset: Unplug the unit for 5 minutes, then plug back in and try again. If E01 returns, continue.
• 2. Inspect power and outlet: Verify the outlet has 120 V (or 230 V for your model) and is not on a tripped GFCI. Try a different outlet.
• 3. Access heater circuit: Remove the rear or bottom service panel (varies by Bunn model such as Heat N Brew, Infusion, or commercial CW series). Look for the tank heater terminals on the stainless hot water tank.
• 4. Check wiring: Inspect the heater wires and spade connectors for burning, discoloration, or loose connections. Reseat any loose connectors firmly.
• 5. Test heater element: With the unit unplugged, disconnect at least one heater lead and measure resistance across the heater terminals with a multimeter. A typical Bunn tank heater will show a finite resistance (often 10–40 Ω). If it reads open (OL), the heater is failed and must be replaced.
• 6. Check high-limit thermostat: Locate the manual-reset high-limit thermostat (usually a small round device mounted to the tank with two terminals). Test for continuity. If open and has a reset button, press it firmly until it clicks. If it will not reset or remains open, replace it.
• 7. Control board relay: If heater and high-limit test good but E01 persists, the control board heater relay may be defective. Inspect the board for burn marks. Replacement of the control board is typically required.

When to call a technician: If you are not comfortable testing live voltage or replacing the tank heater or control board, contact a Bunn-authorized service technician.