If your Bosch dishwasher not heating water, and it washes with cold water only, the issue is usually in the heating system or its control circuit.
This is a common problem and often fixable without replacing the whole machine.
Quick Answer
Cold washing usually means a faulty heating element, relay, or pressure switch issue. Start by testing the heater and checking the control board.
Step-by-step fix for Bosch dishwasher not heating water
Step 1: Confirm the problem
Run a cycle and check:
- Is the water cold throughout?
- Are dishes not drying properly?
👉 If yes, the heating system isn’t working.
Step 2: Test the heating element
This is the main component.
- Turn off power
- Access the heater
- Use a multimeter to measure resistance
Typical values:
- ~10 ohms (120V models)
- ~20–30 ohms (230V models)
👉 No reading = faulty heater.
Step 3: Check the pressure switch
Bosch dishwashers won’t heat unless:
- Enough water is present
- Proper pressure is detected
👉 A faulty pressure switch can prevent heating even if the heater is fine.
Step 4: Inspect wiring connections
Look for:
- Loose wires
- Burnt connectors
- Corrosion
👉 Poor connections can stop power reaching the heater.
Step 5: Check the control board relay (very common fix)
This is a key issue in many Bosch models.
- The relay controls power to the heater
- It may fail or develop bad solder joints
👉 Replacing the relay (cheap part) can restore heating.
Step 6: Look for cold solder joints
On the control board:
- Inspect relay area
- Look for cracked or dull solder
👉 Reflowing solder can fix intermittent heating issues.
Step 7: Reassemble and test
After fixing:
- Restore power
- Run a hot cycle
👉 Water should now heat properly.
Extra tips and best practices
- Always disconnect power before testing
- Take photos before removing wires
- Use correct replacement parts
- Keep dishwasher filters clean for proper pressure
Common mistakes to avoid
- Assuming the heater is always the problem
- Ignoring the relay or control board
- Skipping pressure switch checks
- Not testing with a multimeter
FAQ
Why is my dishwasher washing but not heating?
Because the wash system works independently, but heating requires proper signals and power.
Can a relay really cause this?
Yes. A faulty relay is one of the most common causes.
Is this repair expensive?
Usually no. Relay replacement is cheap, and heater replacement is moderate.
Conclusion
If your Bosch dishwasher does not heat water, focus on the heating element, relay, and pressure system. Many cases are caused by a simple relay failure rather than a major component.
With proper testing, you can fix this issue and restore full performance.
Reference links
https://www.repairclinic.com/RepairHelp/Dishwasher-Repair-Help
https://www.searspartsdirect.com/diy/repair-guide/how-to-fix-a-dishwasher-that-wont-heat
