Just got this vehicle so the history is mostly unknown.

This 86 300E has two outstanding issues. Are they related?

The first issue is:

The alternator does not charge the battery. I realize this may be a faulty alternator. Vehicle starts and runs well but discharges and stalls after 1/2 hr of running. Freshly charged battery reads 12.45V but drops to 11.36V at idle. Voltage drops with increased rpm. .......Alternator is obviously not charging. How can I test the alternator with the alternator in the vehicle? I am not familiar with this specific alternator but I assume it has a field coil circuit that passes through brushes. I also assume it has a replacable reg/rect. Does anyone have a wiring diagram of this charging system so I can test the alternator with a multimeter?

The second issue is:

The bank of warning lights on the lower left side of the dash do not light up when the key is turned on. Are they on a common fuse, is there a common ground that might be at fault, or is it coincidental that they are all out at the same time?

These seem like two separate unrelated issues. But, on my 86 BMW 325E when the alternator warning light burned out it PREVENTED the charging system from charging the battery. Once the warning bulb was replaced the battery charged well. Does Mercedes have a similar issue?

Thanks for any help!