Mondeo Undervoltage Detected

I had a similar problem with my Mondeo. It sounds like a battery voltage issue or something draining your battery when the car is off. Have you checked the voltage regulator? Those can cause havoc if they're not working correctly.

Thanks for the quick reply! Where exactly is the voltage regulator located? And is there an easy way to test if it's faulty before taking it to a professional?

Without the proper equipment, testing the voltage regulator isn't straightforward, it's embedded in the alternator. Given the symptoms you're describing: 'undervoltage detected', 'Vehicle start poorly', 'Failure of various systems in the vehicle', 'Weak or flickering lights', 'Weak battery when starting the engine', and the high mileage of your car, a heavily discharged or defective battery is a possible cause. I recommend taking it to a workshop to get it properly diagnosed and avoid further electrical problems.

Thanks for the advice! I took it to a local mechanic, and you were right – it was the battery! Apparently, it was heavily discharged and defective. They replaced it, and the 'undervoltage detected' warning is gone. The final repair cost was 290€. Everything seems to be working fine now.