W201 / W124 alternator questions.

[quenching]

I suspect the alternator in my W201 '84 2.0 petrol 190E is not behaving as it should and may need replacing. Now rather than buy one and turn out to be wrong I thought I might try and swap it for the alternator from my W124 '94 E220. Are they a straight swap or is there more to it than that?

The part number on the W201 alternator is 0120489300, a Bosch unit, haven't had a chance to get to the W124 yet but I'm guessing that as they're 10 years apart they're unlikely to have the same part number.

From reading other posts it seems that alternators also have a regulator as a separate plug-in part, is this a better part to start replacing if the voltage output from the alternator seems too low?

Obviously I know very little about alternators

 

[Ted]

The regulator is the least reliable part of an aternator. They are cheap and easy to replace (plus they come with a 'free' set of brushes.
I would start with that.

 

[grober]

Doubtful if your 190 and 220 ALTERNATORS would be interchangeable without changes to the mounts and or electrical connections. Best to get to get a regulator pack as suggested. However if the alternator is an original 84 it may well be worth considering a complete rebuilt/exchange unit

 

[quenching]

Thanks for the advice gentlemen, I've had a look at the alternator in the W124 E220 and as expected its a different part number, difficult to tell if it would fit the 190 without removing it to check connections and bolts etc, so I'll get a new regulator and see it that fixes things. The current alternator in the 190 is a 55A one, if it needs replacing I presume a 70A one is a suitable replacement as there is a more powerful radio and subwoofer fitted?

Do alternators need fixing/replacing only as a result of wear due to mileage or is age also a factor? My 190 has only done 37k miles but is 27 years old.

According to this page the regulator for my alternator is this one, it certainly looks like mine, is the small black square thing with FX 224 on it a capacitor of some sort and if so what's its purpose? This is a photo of mine in case anyone finds it useful in the future:

 

[Dieselman]

They are indeed the regulator and capacitor (suppressor). The cap stops arcing and electrical noise.

The regulator/brushes/diode pack can just wear out with age as well as mileage.

 

[grober]

Have a look at this video.[YOUTUBE]WYvZRz5Truo[/YOUTUBE]

 

[quenching]

Thanks Graeme, isn't this internet thing bloody marvelous!! Very much appreciated