2008 R52 N/A, 130k AT, stock
in troubleshooting a nightly battery drain (11.7v down to 9.1) I discovered the alternator is overcharging at idle,showing 16-17v measured directly off the battery. This alternator (110amp) tested good at my local AP store, as does one I pulled from the local JY from a 2003 justa (120 amp). The 120a is larger, meaning the pulley iut is farther from the other pulleys. Can I use this 120a with a belt from a 2003 justa?
TIA

 

https://www.northamericanmotoring.co...lternator.html

it fits the same belt, its been converted to the 110A already it will have the power cable 12427534704 and 12517534705 , bolts 07130770522 and https://www.ecstuning.com/b-genuine-...h/12317516819/

I would swap the regulator first to see f that is it. But the regulator is not available for the 110, just the 100 and others. Do you have a part number off that 110 regular?

https://www.ecstuning.com/Mini-2008-...ne/Electrical/

 

swap the regulator.....why? to see if it's bad? it showed over 16v at the battery while the car was idling, with xenons on. It's bad.....The battery continued to drain overnight with all fuses and relays in place, and the alternator removed, and radiator fan removed. I'll probably end up replacing alternator and adding a quick disconnect to the neg cable at the battery to limit battery drain.

 

Regulator controls the Voltage and when the voltage goes out of wack that can be it. Should be near 14vs-13vs at idle. Most people just swap the who alt to new because when the regulator goes and its high miles sometimes the bearing might have some wear on then and start to make noise down the road.
On the drain overnight, it might be connected to that, or the battery being shot from overcharge? Or a short in the system ( bad aftermarket alarms, stereos, rally lights..etc) Bad alts will ruin the battery over time.

 

Battery is new interstate, still tests good. It replaced a 2.5 year old Exide, assumed to be bad

 

Even load tested, just not measured by voltmeter? Local interstate battery places can swap them out and load test them just to check its not a bad cell or something.

 

Battery is new interstate, still tests good. It replaced a 2.5 year old Exide, assumed to be bad
The new one may be worth testing again