Could i replace the alternator on my 1995 318i its 80 amps to a 140 amp one. Also the reason I'm replacing it is because someone told me the bearing is going bad so it whistles is that true?

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW Alternator Troubleshooting and Replacement

In theory, the alternator should only supply as much current as is drawn by the system. In other words, if you have an 80 amp unit and your draw is only 40 amps, then you can use anything above 40 amps and it will be fine. People typically install a higher amp alternator when they are installing a big stereo system, or higher power headlamps. So yes, installing a higher output unit should be fine.

On some more modern cars they will sometimes trigger an alternator lamp when you install a higher amp unit as they are not expecting the alternator to be charging above it's expected level.

- Wayne

I just replaced my 80 amp with a 140 amp on a 96 328i Sedan. Only 4 days out. but the difference is amazing! But like Wayne said, all components will only draw what they need, so the load on the 180 amp shouldn't be any more than what was on the 80 amp.

But, you will probably need bigger bolts & nuts (if your car has threaded mounts better scope it out well before purchasing the 180 amp). The 180 amp will have bigger mount holes.

I had to replace the lower mount bolt with a 14mm (was 12mm), and it also has to be about 40mm longer. The upper bolt hole on the 180 amp unit, because it was bigger, required an insert, or sizing sleeve, to take up the slop. I had to use the original 12mm up top because the alternator mount housing is threaded, so there was no choice.