2006 MINI Cooper S –automatic 104,000miles Quick version: My alternator failed. I replaced it with a reman Denso and also replaced the battery and belt tensioner and belt. Did some testing to see if there were any bad grounds or any other problems other than the alternator before I replaced it so most Pos and Neg contacts were checked.Everything seems back to normal but now that I am monitoring my voltages this is what I am seeing with a voltmeter at the lighter socket.Is this normal for these cars with R53 DME controlled alternators? Is the DME in fact shutting the alternator down at lower RPMs to protect it from high current draw?

Condition.......................... no load...... w/AC on...... Power steering load .......w/Cooling fan on
Start up ..............................14.1 v......... N/A ......................N/A................................. N/A
Idle in Park 800 RPM.......... 14.0 v .......11.8-12.5 v............... 12.2v ...........................12.3 v
2000 RPM ...........................14.0 v ........13.6 v .....................N/A .............................13.9 v (parked)

Thanks

Tom

 

Tommy
I'd say that's about right.
My 2002 Cooper S is pretty similar.
As long as you see 14.1 - 14.2 driving around normally, even with the headlights on, I think you're OK.
At idle with the A/C on I do see the same low voltages - it wanders around quite a bit but I wouldn't expect much more at idle.
I'd say you're fine.

 

Mine is about the same. I'll see 14+ at idle, no AC. As soon as AC is on it will drop to 12+ then engine will idle up to ~1k and see ~13.5v. Once im moving its up to 14. All voltages are with and without lights & accessories. Caveat....voltages are from OBD reader.

 

quote: Is the DME in fact shutting the alternator down at lower RPMs to protect it from high current draw?: end quote
I think the rpm are not enough at idle to supply the 14.2 volts the DME wants to have.