Driving home this evening (dark, headlights on) 50 miles from home my Turbo 1987 300d "antilock" dash light came on. (124 body-603.960engine) Soon there after I notice my gage lights becoming dim. Headlights are next noticed and finally the dash board symbol for lights comes on.
Having pulled off the road, with engine running the radio and other electrics slowly go away. Checked under the hood and inspected- spun all fuses. I did NOT confirm that the belt was present and working properly; but I recall, it did appear to be in good condition at last oil change.
So, supposing it's not the belt, when I drive the 50 miles to the car in the morning, should I have an alternator and-or a regulator with me???? Will these fix the problem? If I buy only the regulator, can it be installed without removing the alternator?

 

The first thing I would take is good battery.
Without headlight on, good battery would get you 50 miles with something to spare. Actually the diesels with vacuum shut off will run without any electricity.
Than at home you can play with troubleshooting whatever it is.
Than in case it is a belt. Without belt turning the water pump and fan you won't make more, than few miles.

 

Thanks Kaj,
Of course, I wasn't thinking of the overheating factor! Coolant temperature was steadily just over 80c, as usual. I can say with confidence that the belt is therefore present and intact. In contemplating the state of the dashboard warning lights; the night before this failure, when I returned home late, with the car off, I recall seeing the battery light on the dash glowing ever so slightly.......? Started up friday morning without a glitch.
I'll be driving the 50 miles back to the Benz in my back-up car, and thus will be doing all troubleshooting and repair onsite.

Can the regulator on this car's alternator be replaced? If so and I buy only the regulator, can it be installed without removing the alternator?

 

yes.

lock the carbon brush with a small pin before inserting.

 

Thanks Sleep! After further consideration, I have chosen to replace the entire alternator.
The car is home thanks to a new Battery, ala Kaj's recomendation, Cheers Kaj!

Next Question is:

How do I loosen the serpintine belt which is holding the alternator and preventing removal?

In the motor's centre there appears to be a tensioner. Two shock absorber like devices are attached to this tensioner and the motor.

Thanks again for the information. I'd performed a search here for "tensioner" but only hit timing chain tensioner posts.

 

I did the job on 93 model. The tensioner had a big hole on its side, where you could stick back side of Lugwrench, or other bar and pull the tension off. At this point the belt just slides out.