Q: I'm trying to figure out the manufacturing date for my Mercedes battery.

If you see a letter followed by two digits that is "replace before date". The letter signifies the month and the number signifies the year. For instance, if the code is D19, the expiration date is April, 2019. However, if you suspect a bad battery, the code will not help. What you need is an actual test of battery condition such as a load test.

If the battery passes a load test, and yet the starter does not function, first be sure that the engine immobilizer system is not activated thus preventing the car from starting. If the engine is not turning over (cranking) with the key held in the start position, that means that there is a problem in the starter and/or the starter circuit. If there is no starter motor operation at all with the key held in the "start" position, the procedure is to test for power and voltage drops to the starter motor/solenoid. If there is no power, or a large voltage drop is measured, then the electrical circuit supplying the starter motor has a fault. The circuit that will have to be tested begins at the battery and includes grounds, wiring (some of which is very heavy cabling), fuses, relays, the ignition switch, neutral start switch, and terminations. On the other hand, if the starter is getting power with the key in the "start" position, and yet the starter doesn’t work, then the starter is replaced. Note that starters can and sometimes do develop intermittent faults due to bad spots on the armature. If you want the required diagnostic steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a no start diagnostic and the responding certified mechanic will get this no start issue resolved for you promptly. Please let us know if you have further concerns or questions as we are always here to help you.