70A alternator for 280SE 3.5
 

While removing some parts from a later 450SLC I noticed the alternator support/bracket is different from the earlier M116/117 engines and it interested me because I would like to install a larger alternator than the 55A unit on my 280SE 3.5. I looked under alternators for a '79 450SLC and there are 3 Bosch units from 55A to 70A. so the question is could I install the 450SLC bracket on an earlier engine and use the 70A alternator? Is it plug and play? I cannot compare the connections since a lot of my project is stored.

I know my 72 4.5 alternator has external voltage regulator but I know the later 450SLs had integrated voltage regulator. Not sure when the change was made but that would require some modifications.

Tony,

I had the original alternator in my 72 280se 4.5 changed out to this one a couple of years ago. The new unit is rated at 90A or 95A. I cannot recall the actual rating, but it is much more than the 55A unit it came with.

The other plus is that it looks OE.

https://www.ebay.com/itm/Mercedes-Alternator-1970-1973-AL72X-Generator-/253194184262

I put a modern GM alternator on mine. Never mind the amp rating (I think this one is 100amp), but modern alternators put out 14.5 volts, while the old Bosch units top out at about 13.7. It may not seem like a big difference, but everything works a little better with a bit more voltage.

Can I see a picture of the GM alternator installation? I emailed the Ebay seller about the AL72X-he said it is the standard 55A alternator I already have. But for $225 he will build a 85A-seems like a lot but I want the appearance to look correct. Yea I don't like the lights dimming when the engine is idling-one forgets that's just the way cars used to be.

Have you taken one apart to see if you can source higher amp windings easily? Sometimes it's as simple as swapping out those. You can often find winding assemblies online for most alternators. The hardest task would be finding a higher amp one that fits.

Tony,

I paid that guy either $149 or $169 + shipping for the 90/95A alternator. He had it on Ebay already built, perhaps that is why it was cheaper. This was back in 2015 if my memory accurately serves me.

Did the VW Quantum/Audi 4000 not have the same type of alternator as our cars but rated at 70A?

Do you have a local company that can rewire your current unit to a higher amperage?

Thanks-I have just begun my quest and in the learning stage. it seems some are using Saab alternators but as you mentioned I'm sure there are others that will fit

Tony, did you ever figure out a solution to your alternator quest? Mine is dead and I am looking to significantly upgrade but like you I'd like it to not stand out. I'm willing to sacrifice specific OEM look for effectiveness as I like to drive my 3.5 as much as possible.

It's been a while since I looked at this and I have not made it to the point of purchasing anything but the Pick n Pull 450 alternator/mount to experiment with but there are 120 and 150 amp alternators available for the 450 models-look on Ebay. If I recall the 450 alternator will not fit in the 3.5 alternator mount so you would need a 450 mount. The mount might need some modification to correct for a slight belt misalignment due to different width. There might be other ways to go but this seems pretty simple and mostly bolt on.

Thanks, Tony. I'll report back after I make a move on this. I'm running Pertronix Ignitor II as well and while it's been pretty good the RPMs still don't match up right (even after trying different methods) and the engine cuts fuel now at around 4500-5000 for each shift. Different problem but one thing is certain I need a much higher amp alternator to deal with aftermarket AC and general purposes. Again, I'll update after I make a move.

Nothing in the D-Jet would cut fuel at a given RPM, or shifts, which tells me there may be some other issues.
If you keep your foot in it, does it rev past 5k? Or does it just not go past 5k and shift?
Be as thorough as you can, and I'd suggest making a new thread... it almost surely isn't electrical related (Unless you're putting a voltmeter on and see you're like 10V or something ridiculous at 5k RPMs).

There might be a rev limiter distributor rotor installed-pop your distributor cap and take a look. How do you know it's fuel and not ignition?

It absolutely could be ignition over fuel. I have some sorting to do on this and can't wait to get to the bottom of it. Never grow tired of this car. Aren't we lucky we bought ours way back before they took off?

Yea I bought mine almost 20 years ago. I can't wait to get going on it. The only miles it's done lately is on a trailer.