The instantaneous water heater is the flow-through heating element inside your Bosch coffee machine that heats water to precise brewing temperature on demand. When the heating element burns out, the thermostat fails, or scale buildup causes the heater to overheat and trip its thermal cutout, the machine stops producing hot water — resulting in lukewarm or cold coffee, no steam, or a machine that powers on but never completes a brew cycle. The 12006343 Bosch OEM Instantaneous Water Heater is the factory-specified replacement that restores full on-demand heating and precise temperature control.
✓ Symptoms This Fixes
- Coffee machine brewing lukewarm or cold coffee
- No hot water dispensed when hot water function is selected
- Machine powers on but does not complete a brew cycle
- Heating indicator light stays on but no heat is produced
- Machine takes significantly longer than normal to heat up
- Error code or heating fault displayed on the control panel
- Machine worked intermittently before stopping heating entirely
- Coffee output is watery or under-extracted due to insufficient brew temperature
✓ Part Details
- OEM Part Number: 12006343
- Brand: Bosch OEM
- Component: Instantaneous water heater (flow-through heating element / thermoblock)
- Compatible Model: BCM8450UC
- Genuine OEM: Yes — factory-specified replacement
- Options: New or Used (inspected and tested)
Scale buildup is the leading cause of instantaneous water heater failure in coffee machines — mineral deposits insulate the heating element, causing it to overheat and trip the thermal cutout (a one-time safety fuse). Before condemning the heater, locate the thermal cutout on the heater body and test it for continuity with a multimeter. If it reads open (infinite resistance), the cutout has tripped — on some units this can be reset; on others the heater must be replaced. Either way, run a full descale cycle after installation using Bosch-approved descaler to remove the mineral deposits that caused the failure. Skipping the descale will cause the new heater to fail by the same mechanism within months.
✓ Installation Notes
- Skill Level: Intermediate to Advanced — requires machine disassembly and handling of water and electrical connections
- Estimated Time: 45–75 minutes
- Key Steps: Unplug machine and allow to cool completely → Remove outer housing screws and lift off casing → Photograph all water line and harness connections to the heater before disconnecting → Release hose clamps and disconnect inlet and outlet water lines (have towels ready for residual water) → Disconnect electrical harness connectors from heater terminals → Remove heater mounting screws or brackets → Seat new heater in same orientation → Reconnect water lines and secure clamps → Reconnect harness connectors → Reassemble housing → Run 2–3 water-only cycles before first brew to purge air and confirm no leaks
- Safety: Always unplug the machine and allow it to cool fully before opening the housing. Never work on a live appliance. Confirm all water line connections are secure and leak-free before restoring power — a loose hose clamp inside the housing will cause water damage to the control board.
✓ Compatible Models
Bosch: BCM8450UC
Contact us with your full model number to confirm compatibility before ordering.
✓ Why XPart Supply
- Canadian Business Since 1996 — 30 Years of Appliance Parts Expertise
- Guaranteed Fit — OEM parts matched to your exact model
- Fast Canada-Wide Shipping
- Trusted by DIYers and Appliance Technicians Across Canada
- Expert support to confirm compatibility before you order
✓ Frequently Asked Questions
How do I know if the heater has failed or if it's a scale/blockage issue?
Test the thermal cutout on the heater body with a multimeter set to continuity or ohms. A good heater reads a low resistance value across the element terminals. An open reading (infinite resistance) on the element means the coil has burned out and the heater must be replaced. An open reading on the thermal cutout specifically may indicate a tripped safety fuse rather than a burned element — check your service manual to determine if the cutout is resettable on your model.
Will descaling fix the problem without replacing the heater?
If the thermal cutout has tripped due to scale-induced overheating but the heating element itself is intact, descaling and resetting the cutout (if resettable) may restore function. If the element has burned through, descaling alone will not fix it — the heater must be replaced. In either case, always descale after repair to prevent recurrence.
What is the Used option?
The Used option is a genuine Bosch OEM instantaneous water heater pulled from a working appliance, tested for element continuity and thermal cutout integrity. Ideal for machines where a new part may outlast the appliance.
Does XPart Supply ship appliance parts across Canada?
Yes! XPart Supply ships OEM and aftermarket appliance parts Canada-wide with fast, reliable shipping. We've been serving Canadian appliance repair customers since 1996 and offer guaranteed fit on all parts. Contact us if you need help confirming compatibility with your model.
✓ Model-Specific Repair Pages
✅Compatibility & Cross Reference
Not sure about your model number? Call 1-877-899-7278 and we’ll help you confirm. All brand names are the property of their respective owners and are used for compatibility reference only.
Buy Online Pick Up In-Store
Kitchener, Ontario N2E 1W8
- Choosing a selection results in a full page refresh.
