Dryer runs but does not heat; E03 appears after a few minutes of operation.

Safety first: Unplug the dryer. Heating components can remain hot after shutdown; allow time to cool.

• Confirm no heat: Run the dryer on a high heat program for 5–10 minutes. If the drum turns but air remains cold, proceed.
• Access heater assembly: On many Gaggenau condenser/heat pump dryers, the heater or heat pump module is at the rear or base. Remove the rear panel or lower access panel as per the service manual.
• Inspect wiring: Check all connectors to the heater element, thermostats, and NTC sensor. Reseat any loose plugs and look for burnt terminals.
• Test heater element: Disconnect the heater and measure resistance with a multimeter. An open circuit indicates a failed element that must be replaced.
• Check thermostats and NTC: Test the high-limit thermostat and safety thermostats for continuity at room temperature. Replace any that are open. Measure the NTC sensor resistance and compare to Gaggenau specs; if out of range, replace.
• Reset and test: Reassemble, restore power, clear the error by unplugging for 5 minutes, then test a cycle. If E03 returns with all components good, the main control board heater relay may be defective.