I am experiencing a charging problem with my 2004 S430. I rebuilt the battery and alternator in January of this year, and it has functioned well until now. Last week, unexpectedly, the voltage significantly decreased when using the vehicle. I had to remove the battery and recharge it three times to get home. The battery maintains a voltage of 12.6 volts, suggesting it is functioning well.
I possessed a guarantee for the alternator, therefore I placed an order for a replacement. I substituted it, nevertheless the same problems persisted. Upon first activation after a period of inactivity, I see a voltage of 14V, which thereafter diminishes progressively. The voltage is consistent at the battery, the fuse box under the carpet, and the alternator terminal when the engine is operating. I verified that the blue wire connected to the alternator has 12 volts when the engine is operating. Is this a problem with the prefuse junction box? Is there anything else I should verify before to placing the order?