Previous owner told me that he replaced the alternator with an Advance Auto Parts version, approximately 1 year ago (and before I bought it).

2012 MCS R56

Currently (ha) voltage swings between 12.5 and 16 - probably a bad voltage regulator and I'd like to replace the whole alternator (which includes the regulator).

My question, if anyone wants to weigh in: how can I tell if the car takes the Valeo 120A or Bosch 150A? Two MINI dealers have told me that it could be either one (they looked up the VIN), realm.com shows that it could be either one, and the only number on the current replacement one in the car now is "AL1904". (I haven't taken it out yet, but spent a lot of time with an inspection mirror.)

One dealer said that 75% of the ones they sell/install are the Bosch, but if it's supposed to take the 120 it might cause problems.

Anyone have any experience with this or any ideas of how to find the answer? Thanks!​​​​​​​

 

fwiw - my 2009 MCS used the 120amp Valeo alternator...

 

I've not seen the two side by side to compare... Are the electrical connectors the same? If they are, I would just replace with the 150A versions. Voltage output should be the same, but you'll have a higher available capacity.

 

The same connector fits on both the 120 and the 150, but the two alternators look different. Unfortunately, the alternator thats now in my car doesn't resemble either one.

Both dealers and an independent mechanic told me that the wrong amperage alternator will cause havoc with the electrical system. I don't know why that is, exactly, but I'm trying to not take that chance.

 

The 150 amp has a black stripe around it, looks like you're does not. My 12 R56 had the black strip.

 

Someone on a german Mini forum posted in 2017 the response of an authorized BMW dealer (regarding a price estimate for having the alternator and battery replaced). The dealer explicitly wrote that the only way for him to identify the required alternator (120A or 150A) is to actually remove it from the car. He also stated that most cars were fitted with the 150A variant and gave prices for both (the 150A one being about 17% more expensive than the 120A).

The post is here:
https://www.mini2.info/showthread.ph...423#pid2702423

Whether true or not I can't say. I haven't found any other relevant information about this on the german forum, though.

Removing and visually inspecting the alternator will of course be of little use if there is no guarantee that the correct one was fitted when the previous owner had it replaced...

 

Both dealers and an independent mechanic told me that the wrong amperage alternator will cause havoc with the electrical system. I don't know why that is, exactly, but I'm trying to not take that chance.

amps too LOW can be an issue and the fix is usually to install a more powerful power source (like a bigger alternator)

but amperage is based on what is 'drawn' and the maximum amount that you can draw from a circuit so there's no such thing as too much (within reasonable limits). For example, you can easily install bigger battery for starting .. you can't have too many cold cranking amps!

Or another way to look at it. Your house probably has some 10 amp, 15 amp and 20 amp circuits. Plug too much into a 10 amp and you blow the fuse/breaker. But if you have only one small item on a 20 amp circuit, is there an issue? No .....

If in doubt, go for the higher output . . .

*****************************
ask Google: too many amps?

Will too much amperage hurt a device?
A higher voltage than a device is designed for will most likely blow up some components, but amperage is derived from how much current is actually drawn, based on the device's resistance, so having “too much” is not a problem and will do no harm.

 

Yeah, AMPs in an alternator refer to its capacity, not its actual output. I would have no reservations putting the 150A alternator in place of the 120A version.

 

Hi George - thank you very much. My German is so rusty now that I could only vaguely understand the post you referenced, but I really appreciate the effort.

I do with there were some way that we could tell which alternator belongs in the car. I haven't been able to find anyone who knows anything more than "we examine what is in there." Something about the computer or electronics must be different if it's true that the wrong alternator causes problems.

Thanks again.

 

This is perfect logic, and I agree with it. However, I'm hesitating because MINI mechanics and dealers have told me that the wrong alternator causes problems. I agree with the logic that it shouldn't, but I'm trying to figure out the right way to do it. Thanks!

 

From newtis, quote:
"The installation of the alternator type depends on the engine used and on the vehicle equipment."

This does not sound like it was purely a matter of coincidence or availabilty.

If the statement by that BMW dealer is correct, it would mean that:
- the "formula" they used to determine which alternator needs to be fitted in any given car has been lost or is no more applicable and
- no records in respect to which alternator type was actually fitted to each individual car exist any more

All the while both detailed parts lists and VIN decoder databases for these cars do exist and are publicly accessible.

 

Many people upgrade their alternators with no side effects. I'm wondering why you want to replace it? Voltage swings are normal for newer cars, the ECU turns it on and off to be more efficient. Very rarely do you see them on continuously.

 

it is pretty common that during the 'life' of a model it begins with an amp load of X and of course the car is built with JUST enuf amp out put to meet this and limited expansion.

as time goes on, and features are added and even the standard equipment list grows the amp load goes up and EVENTUALLY they MUST begin to provide more AMPS via an alternator with more output.

It is not the least bit unusual for the new LARGER OUTPUT alternator to REPLACE the original part in the catalog entirely rather than stock two units ..... as is the case with MANY redesigned or upgraded parts ...

 

Do you have any codes stored? Anything on the dash indicate a problem is happening? How old is the battery? Do you have the battery health device on the negative terminal that might need resetting? If you aren't having any problems then replacing a 1 year old alternator seems like a waste of time and money. It is straightforward but a slight pain in the butt, as are most tasks on this vehicle. We had to take the bumper off.