Thermador Oven: error code 43 during preheating

Professional Repair Guide

What is this symptom?

If your Thermador oven displays error code 43 during preheating, it indicates a fault detected by the control system, halting the preheat cycle. Common causes include cooling fan issues, temperature sensor failures, or control board malfunctions. Understanding these can help you troubleshoot effectively.

Urgency: Medium

Important Tips for Thermador Models

  • Thermador official error code documentation does not publicly list code 43, so detailed definitions come mainly from repair communities and expert discussions.

Possible Causes

Cooling fan fault or airflow detection failure

How to Identify: Error appears when fan doesn’t run or the airflow detection switch/sensor isn’t triggered during operation; visual inspection may show stuck fan blades or misaligned switch. Oven overheats internally without adequate cooling.

Part: Cooling fan / sail switch or Hall effect airflow sensor

Temperature sensor fault leading to safety shutdown

How to Identify: Oven heats then shuts off with code 43; temperature sensor resistance deviates significantly from ~1080 ohms at room temperature when tested with a multimeter.

Part: Oven temperature sensor (RTD/probe)

Control board or fan relay/control circuit failure

How to Identify: Cooling fan appears to run properly and temperature sensor tests normal, but code persists; checking relay output or power to fan may show control board isn’t activating fan correctly.

Part: Control board / fan relay circuit

DIY Solutions

Inspect and clean cooling fan and sensor/switch

Moderate 30-60 minutes
Tools Needed: Screwdriver set, Multimeter (optional)
  1. Turn off power to the oven and disconnect from mains.
  2. Remove the back panel to access the cooling fan assembly.
  3. Visually inspect the cooling fan for obstructions, debris, or stuck blades; clear any blockages.
  4. Check the sail switch or Hall effect airflow sensor alignment and reposition if misaligned per repair guidance.
  5. Reassemble and restore power, then test by initiating preheat cycle.
⚠️ Safety First: Ensure the oven is de-energized before accessing internal components.

Temperature sensor resistance check and replacement

Moderate 30-90 minutes
Tools Needed: Screwdriver set, Multimeter
  1. Disconnect power to the oven.
  2. Locate the temperature sensor (usually inside the oven cavity mounted near the back wall).
  3. Disconnect and measure resistance at room temperature; compare against expected value (~1080 ohms).
  4. If resistance is significantly out of range, source the correct replacement sensor for your model and install it.
  5. Restore power and test oven preheat cycle.
⚠️ Safety First: Testing with a multimeter requires familiarity with electrical measurement.

Professional Repairs

Replace cooling fan assembly or airflow detection components

Estimated Cost: $150 - $400

Control board relay or main board repair/replacement

Estimated Cost: $300 - $800

When to Call a Professional

If the cooling fan motor needs disassembly or replacement
If the temperature sensor is not easily accessible or tests inconclusively
If control board diagnosis and replacement is indicated

Preventive Maintenance

  • Clean cooling fan and vents: Airflow obstruction issues that may trigger error codes
    Frequency: every 6 months
  • Inspect temperature sensor resistance periodically: Temperature sensor drift or failure
    Frequency: annually

Frequently Asked Questions

Why is my Thermador Oven error code 43 during preheating?
Error code 43 indicates a detected fault, often due to cooling fan or temperature sensor issues.
How do I fix Thermador Oven error code 43 during preheating myself?
Check the cooling fan for blockages and test the temperature sensor's resistance.
How much does it cost to fix error code 43 during preheating?
Professional repairs can range from $150 to $800, depending on the issue.
When should I call a technician for error code 43 during preheating?
If DIY solutions don't resolve the issue or you're uncomfortable with repairs, it's best to call a technician.

References & Sources

Community Analytical Insights

Analysis based on real user discussions from appliance repair communities

Can I Fix This Myself?

65%
DIY Success Rate Difficulty: Either

Common Issues Reported by Users

  • Faulty temperature sensor
  • Malfunctioning control board
  • Wiring issues or loose connections

User Suggested Solutions

  1. Check and replace the temperature sensor. To do this, unplug the oven, locate the temperature sensor (usually at the back of the oven cavity), disconnect it, and replace it with a new one. Reconnect and test the oven.

  2. Inspect the control board for any visible damage or burnt components. If found, replace the control board. This may require removing the back panel of the oven. Ensure the oven is unplugged during this process.

  3. Check all wiring and connections to ensure they are secure and undamaged. Look for any loose wires or burnt connectors. Tighten or replace as necessary.

Analysis based on 1 community discussions
View Sources

Data compiled from real discussions on r/appliancerepair and r/Appliances:

  1. Thermador Oven - Error 43

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