80A vs 140A alternator

[m3f_Synenergy52]

Hate to bring up an old thread but my M3 Vert has heated seats and has an 80A alternator. The bearing is making a noise like crickets at low rpms. anyone know of a rebuild kit? or should i just buy a rebuilt? new (rebuilt or refurb--not sure) are going for $140 at alternatorpros.com

[m3f_pbonsalb]

In the E36 or M3 forum at Bimmerforums, someone recently rebuilt an alternator and posted the details. Thread active within the last month.

[m3f_HerrRoald]

Ok I have the same question: can we just throw a 140 AMP Alternator into a 80 AMP? can yo swap them?

[m3f_Richardsperry]

IIRC there are two manufacturers of alternators in BMW's. Valeo and Bosch. Both make 80 and 140A versions. They are not directly interchangeable. If you have Valeo you need to find a Valeo or swap the pulley and spacer from your old one to the new Bosch one.



The alternator doesn't care if the car has HID's or not. it is such a short transient current spike, the battery will handle it. It's more about stereo and lighting loads.



AFAIK, all M3's in the USA came with the 80A unit. I mean 80A @ 13.4V is 1072 W. That's a lot of amps...

[m3f_Diesel///M3]

I've been considering using a 140a as well due to the fact that whenever I put my windows up or down, you can hear s subtle but noticeable decrease in voltage (I guess?) in the radio. I also hear what sounds like a 60 sec cycle hum through the speakers. The car actually shudders slightly when I use the windows. I thought going to the big boy would eliminate this? No?

[m3f_das borgen]

no no, 5!/1! = 5

do what you want with the maths but please, don't divide by zero

[m3f_Synenergy52]

I bought an 80A alternator from alternatorpros.com for $154 free overnight shipping. Bosch. We'll see how it goes! gonna pop it in asap

[m3f_WRXEATR]

FYI I have heated/power LUX seats and my alternator was 80A FWIW

[m3f_Porschetech]

The study of ancient greek and roman civilization and literature in the original greek and latin, as well as in translation. It's basically like English/History/Language combined into one. It was one of the most popular majors back in the day. It's good training for law (my choice) and business as well.

wow!.........now i'm beginning to love ancient history. when i was at school i didn't give a fcuk.



nick, i don't see any problems running a larger alt

[m3f_kablammo]

IIRC there are two manufacturers of alternators in BMW's. Valeo and Bosch. Both make 80 and 140A versions. They are not directly interchangeable. If you have Valeo you need to find a Valeo or swap the pulley and spacer from your old one to the new Bosch one.

I've replaced a Bosch with a Valeo and then back to Bosch with no problems or swapping of pulleys.



From what I've been told you can go to the 140AMP from the 80AMP at will with no adverse affects.



k

[m3f_T2]

Which one weighs more??



Easy guess is the 140A...that would cloud my decision...never had problems putting the top up and down but my alternator too is dying so...has anyone weighed them?

[m3f_pbonsalb]

I've replaced a Bosch with a Valeo and then back to Bosch with no problems or swapping of pulleys.



From what I've been told you can go to the 140AMP from the 80AMP at will with no adverse affects.



k

You have to use the pulley the alternator comes with or should come with -- Bosch pulley with Bosch or Valeo pulley with Valeo due to spacing differences that will otherwise result in poor belt alignment. My rebuilt Bosch 140A came with a pulley so I had no issue, but some are sold without the pulley and that is when problems can arise.

[m3f_pbonsalb]

Which one weighs more??



Easy guess is the 140A...that would cloud my decision...never had problems putting the top up and down but my alternator too is dying so...has anyone weighed them?

Bosch is physically larger and weighs more. Not a lot more but enough to feel. I did not weigh the two.

[m3f_pbonsalb]

I've been considering using a 140a as well due to the fact that whenever I put my windows up or down, you can hear s subtle but noticeable decrease in voltage (I guess?) in the radio. I also hear what sounds like a 60 sec cycle hum through the speakers. The car actually shudders slightly when I use the windows. I thought going to the big boy would eliminate this? No?

80A alternator in good working order can easily handle the power windows. All these cars have power windows and many were fitted with 80A from the factory. Your problem is likely something else, or perhaps just an alternator worn from normal use over time.

[m3f_mmenefee]

For the record, 80A/140A is a _current_ rating. It only matters if you have something to sink that much current. 140A and 80A will behave exactly the same with a 5A load, for example. So unless you're drawing a good deal of power, 140A doesn't buy you much except possibly slightly more drag.


As for HID, your battery will provide the instantaneous current bump to handle your HID ignition. You can weld with a car battery, it will have no problem handling the load unless the wires going to your lights are just too small, or there's some other factor limiting the current. I run HID Boschs and fogs with no issues, and I'm pretty sure I have an 80A unit.


Now, the _voltage_ ratings do have to match (12V system), but since these are both OE spec parts, that part is true implicitly.


Oh, and assuming you meant ! as the factorial operator, 5!/1! = 120.