Display shows E3 and the coffee maker will not heat water.

Safety first: Unplug the coffee maker. Heating circuits carry mains voltage; do not work on them while powered.

• Basic reset: Unplug the unit for 10 minutes, then plug back in and try again. Sometimes an overheat trip will reset after cooling.
• Check for obvious damage: Smell for burnt odor and look through any vents for signs of scorching near the base where the Tristar heating block is located.
• Access heater (advanced): Remove the bottom cover. Locate the aluminum thermoblock or stainless steel boiler with two thick wires connected. Inspect the spade connectors for looseness or corrosion and reseat them firmly.
• Thermal fuse inspection: Many Tristar coffee makers have an inline thermal fuse wrapped in fiberglass sleeving on the heater lead. Check if it appears burnt or open (requires a multimeter). If open, replace with the same temperature and current rating; never bypass it.

Warning: If you are not experienced with mains electrical work, do not attempt to replace the heater or thermal fuse yourself. Contact a qualified appliance technician.