2006 mini cooper S. 113k miles...

I have been working on make it it a reliable daily driver for a year, so far. Now have a problem with alternator charging system I couldn't solve for the last week. Long time forum reader, first post. Hopefully this post may help another reader...

Background.
Began intermittently losing battery charge and power steering. Purchased and installed replacement Denso alternator from FCP Euro. The newly installed alternator charged the battery as expected the first 2 weeks after installation. Then it did not (until today)...

Note, after I took out the prior / original Denso alternator to autozone for bench test. It passed. Urrhhh. I sent it back as core for the newly purchased alternator because the newly installed alternator was working correctly, where the prior ./ original installed alternator was only working intermittently.

Then 2 weeks after I first installed the new Denso alternator, the newly installed alternator stopped charging the battery. The troubleshooting journey started, actions taken / diagnostic information below.

Installed new battery
Fuse 39 ok
Engine ground strap from the body to the passenger motor mount 0 ohms (closed circuit)
Engine ground strip to negative battery terminal 0 ohms (long jumper wire)

I took out the newly installed alternator out of the car and took it autozone. It passed. Urrrhh, but did not work when it was installed in the car.

My alternator had a 3 wire harness connection and 1 high amperage red wire to provide amperage and voltage during charge

Installed my new alternator in the car again after testing at autozone. Alternator still did not work. Urrrh...

Using the attached Bentley service manual I made the following measurements on the 3 wire alternator wiring harness connector. Note, my wiring colors are different that those published by Bentley, and Bentley gives you no information on the voltages on what wires should be during various operating conditions...



I tested the 3 wire harness alternator plug as described below.

Ignition Off
Yellow / Black 0 volts
White / Green 0 volts
White 0 volts

Ignition On
Yellow / Black 12.75 volts
White / Green 12.71 volts
White 0 volts

Engine Running
Yellow / Black 11.12 volts
White / Green 12.30 volts
White 0 volts

I then used used sand paper to clean the surface of the large red alternator copper wire and the surface of nut used to attached the red wire to the alternator. I connected the 3 wire harness plug from prior and testing, started the car, and now the alternator was charging as expected !

The only action I took during many hours of investigation was to clean the red copper charge wire and the nut with sand paper that secured the wire to the alternator.

I am well now well practiced in putting super scooter in front maintenance mode, and googling any mini maintenance site I can find. Let's see how it long it works....

 

It looks like your colors match to me, or did you change your test listing to match?

In case you were wondering...

• The Bentley says you should see battery voltage at the green/white (gn/ws) wire with the ignition on and engine off and also with the engine idling.
• The white wire is a PWM signal to the DME for load monitoring.
• The black/yellow wire runs to the indicator lamp (or its controller, I suppose) from the diode trio. I don't see it in the Bentley, but I'm pretty sure it should be about battery voltage with the key on and the engine off. IIRC, it should be about the same with the engine idling.

 

I’m experiencing a very similar issue in my 2006 r53. Did you resolve your issue, if so, can you share some details?

 

From reading sperscooter's original post, As I understand it; he/she cleaned the large main (red) wire terminal to the Alt which as since solved the issue.
Sounds like like a good course of action when all else has already been investigated.
Best of luck.

 

Appreciate it👍

 

I have this exact issue! Just replaced both the power steering pump and alternator. 10 minute test drive was fine until the very end when the battery light came on and lost power steering! Ordered a long as 10mm wrench to see if can get to that damn nut w/o taking the entire front end of the car off again!

Crossing fingers!

 

No dice...replacing entire NEW alternator.....


And removing AC etc at this point....F'it....

 

Could someone further explain where the large red alternator wire is located? I have been having multiple different issues with my new battery draining after sitting longer than a few days. I installed a brand new alternator even though I was able to drive continuously day after day without any issues.

Now with the new alternator the car made it a 3 hour trip without any issue but on the way back the battery died so I swapped in my backup new battery but it only drove 40 minutes or so before dying while driving. I bought another new battery and charged one of the other new batteries and they each lasted about 45 minutes and I barely made it home.

It seems after the long trip something has caused the new alternator to not charge the battery and I have no idea what to check. I remember plugging in a plug with three wires into the alternator and looked at it and it seems like it is still connected. The passenger side engine ground looks practically brand new.

I do not have the power steering issue people have mentioned and now on top of the battery drain problem now Ive got an alternator charging issue. Before I replaced the alternator one of my batteries built up a lot of corrosion on both terminals which I cleaned off so maybe somewhere in the system there is corrosion or something causing the corrosion but I have no idea what wires to check. If anyone could be a little more descriptive of what to do it would be much appreciated.