Mercedes GLE starting problem

Terminal 30 interruptions on a GLE can be tricky. A discharged battery is common, but intermittent issues suggest something else. Have you checked for parasitic drain? Use a multimeter to measure current draw with the vehicle off. A healthy system should have minimal draw. Also, inspect the main ground connections and battery terminals for corrosion or looseness. A faulty voltage regulator in the alternator could also cause issues. Monitor the charging voltage while the engine is running. It should be around 14V. A significant deviation could indicate alternator problems.

What's an acceptable level of current draw in milliamperes for the parasitic drain test? Also, can temperature fluctuations worsen the intermittent Terminal 30 interruption, especially with a compromised wiring harness?

Acceptable parasitic draw should be under 50mA. More than that needs investigation. Temperature fluctuations can affect wiring harness integrity. Heat can increase resistance in corroded connections, while cold can crack brittle insulation. Given the intermittent nature and the vehicle's age, a comprehensive electrical system diagnostic at a good workshop is advisable. They can load test the battery, alternator, and wiring harness to find the exact problem source.

I took the vehicle to a workshop. They found a defective battery and corroded wiring near the terminal. Replacing the battery and repairing the wiring harness for 290€ fixed the issue.