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What alternate solutions are there in order to fit a bigger Alternator? Or this is not possible at all?

Yesterday evening, with lights, radio, antimist lines, heat, air and wipers on, (plus just a couple of uses of electric windows and locks) the battery almost ran flat in traffic(with the car on!) : I saw the interior lights going darker and the wipers could not move!
It woke up when I revved a bit, so I arrived...
Of course, 3 hours later, I needed cables in order to start the car...

Ok, I understand my battery is 4 y.o. and maybe a bit tired during its life, but I think that I may have overstuffed the car in electrics

(and a second question: shouldn't in theory things be better with the electronic ignition?)

Replaced battery

Seems however that the answer to the problem is the Alternator: It gives 13.5V at idle and with big scale lights on, but with heat on and antimist lines, (and normal lights) it falls to 11.x V

Looks indeed like a alternator problem.
Probably some of the rectifier diodes are blown.


Where there welding jobs done in the past without disconnecting the battery ?

Might, yes..I am not sure

But anyway, the alternator I think has never been replaced or rebuilt all these years
So I guess it is doing very good already for its age...but time to freshen up

Maybe its just up for a new kit of brushes and voltage regulator? Easy swap, or at least check how the current ones look. Always make sure to disconnect the battery before working on an alternator!

Thanks, will check and inform, hopefully by Monday afternoon problem will be solved!

4 years is pretty old for a battery too? Aren't they rated for like 5 years?

It is, yes
It was, actually, the new one is on
Tomorrow going for the alternator

I found that cleaning up where the earth strap connects to the body improved the voltage massively

Good one indeed. I made a brief listing of possible issues and checks for the FAQ section, pls scroll down here:
http://www.bmwe21.net/forum/viewtopic.php?f=38&t=13419

let me know if any suggestions and let us know if you're able to solve your issue now Petros!

Defo will I
At least today,(just back from a daytrip) the car was doing perfect, better than ever! Very torquey, and revving nicely
Like the first days after the ignition conversion

Ok, so here's how the story continues:

The old alternator was removed, was inspected, and the rotor (? right term?) was found corrupted by the years. It seems that this is the reason that, although still working, it could not give "something more" when required. So it was replaced by a new (well, a reconditioned one actually), from "Elstock", I 've never heard of them before (www.elstock.dk)

The new one measured when fitted on the car, is producing 14.1-14.2 V at idling with no other electric charges at all.
When turning on various things, it falls a bit, but always about 13.5, no less, and when a lot of things are turned on altogehter, it goes to 12-12.1 volts

I guess that's OK

however, I was wondering, as my current battery is more powerful than what BMW probably gave with the car, (and I guess that all or most of us choose a better battery, as we have the option to), shouldn't it be combined with an alternator with a larger capacity (for example more Ah? I saw there exist up to 80 Ah for our cars) ?

If anyone knows what upgrades are there available (if any) for alternators, plz help!

I've had numerous E21 alternators and new batteries and they always seem to struggle when you've got a few things turned on, especially at idle. E.g. the other day I had headlights, blower, rear demister, wipers and stereo on - when at idle the headlights could be seen dimming. This is with a brand new battery and VGC alternator.

Nothing weird if the voltage drops at idle, but when moving it should be better than 12V.

What spec alternator and battery do you currently use?

Indeed, the voltage was dropping with the new alternator only at idle.
When revving a bit (around 1500-2000) the voltage was again climbing to 13++

My alternator specs I don't know I 'm afraid-If I manage to read something in there will repost on this.
New Battery is DETA 64Ah, 640A cold cranking