Expedition electrical issues

Greetings. I encountered a similar undervoltage situation with my Ford Expedition. I observed comparable symptoms, specifically related to the charging system which caused voltage drop. It is advisable to measure the battery voltage both at rest and under load. A significant deviation from the nominal voltage (approximately 12.6 volts at rest and 13.7-14.7 volts when the engine is running) would suggest a battery or alternator issue. Have you checked the battery terminals for corrosion or loose connections? These can create resistance and impede proper power supply.

Thanks for the quick response! I'll check those voltages as you suggest. When you say 'under load', do you mean with the engine running and accessories on, like headlights and the AC?

Affirmative. By 'under load', I am referring to the condition with the engine running and auxiliary systems activated, such as the headlights and air conditioning. These systems draw substantial current, thereby placing a significant load on the charging system. If the voltage drops excessively under these conditions, it may indicate either a deteriorated battery incapable of sustaining the required current draw, or a malfunctioning alternator unable to adequately replenish the battery's charge. Given the complexity of modern automotive electrical systems, it may also be prudent to consult a qualified technician to perform a comprehensive diagnostic assessment. In my case I had to go to the workshop, but hopefully you find a better solution.

Much appreciated! I did some more testing based on your advice, and the battery was shot. Replaced it for 290€ and all seems to be back to normal. Thanks again for the help!