Just recently I upgraded the Alternator in my 250SE to 55A. Its made a big difference, and so far I am very happy with the improvement. My 250SE, and nearly all W111/W108 etc, came originally with a 35A alternator.
This seems like a very small size to us now, but when the cars were new, it was adequate. It really only powers the petrol pump and ignition system. The period radios were only a few amps also.
When the mainstream V8 cars came out in 1969 (with the 300SEL 3.5 and 280SE 3.5 Coupe/Cabriolet), they got a 55A alternator. The 6.3 also had this alternator in 1969, but not sure what it had on introduction. Later, this was standardized on the sixes. I can't remember the exact date, but 1971 rings a bell. Interestingly, the 600 W100 had two 35A alternators! This is an externally regulated alternator, that was then carried over to the W114 sixes, and early 107 and 116 v8s.
This would have been combined with more and more people ordering options that used power like A/C, power windows, power sunroof etc etc.
My 250SE was not fitted with A/C when new, but it had been added later. I also do a fair amount of driving it at night, mostly because I don't have any other time to do so.
A couple of years back, my alternator went out. I managed to pick up a rebuilt 35A unit that somebody was selling as they bought the wrong model for their later W108. I had this fitted and it was never really up to the job. Not sure if it was because it wasn't a great rebuild, or if my original alternator (which was marked as 35A) had been rebuilt to a higher capacity at some point.
Last week I had the 55A Bosch factory rebuilt alternator fitted that I bought in from the US. It's the one that goes on a late 280SE, so it bolts right up. Plug is slightly different, but wires are the same and still externally regulated.
it's made a huge difference, and now I can sit in stop/go traffic with A/C on max, headlights on, radio on etc and not have the voltage drop down very low. Car was tuned as well, so the combination of both has it running better than it has for quite some time.
This last week my 250SE has been at the workshop having an alternator upgrade. Back in 2020, my alternator gave up, and I replaced it with a rebuilt 35A alt
www.classicjalopy.com
The other thing I had done last year, was all four calipers rebuilt. I noticed a soft brake pedal and hot wheel. All four were sticky and that has also made a big difference. Given how little many classics are used, I would imagine that most cars have at least rears that are not doing anything much. I use my cars more than most classic owners, and have had this issue on a few cars. Really shows these cars must be driven at least monthly, and properly driven, not just started up.
