The venerable Midlands gave up 3rd gear on my son, so we performed the 6-speed swap. After it was complete, we were getting a battery light, so, a new Valeo-style alternator went in. Still battery light glows happily. Investigation found the cable going from the voltage regulator to the wiring harness was in poor shape. Broken, exposed wires at the VR connector. Repairing wasn't an option, so we ordered the correct cable from our local dealer.

Today, the new cable arrived, yay! We installed it, hooked everything back up, confident our problem was solved. Nope. Our little battery light shone just as brightly as before. *sigh*

Interesting fact, when the cable is unplugged from the wiring harness, no battery light and EVERYTHING WORKS!! When plugged in, headlights flash, AC doesn't work and a host of other problems.

Only thing I can think might be the issue is that we have the wires swapped at the starter after swapping it out, or that our brand-spankin' new alternator is no bueno.

Thoughts?

 

First things first: get your multimeter out and measure voltage when the engine is running. If its not 14.x volt the alternator is bad.

After that check all your fuses and double the grounds, especially the one at the engine.

 

Thanks LukasH. It was on my list of things to check today. Def a bad, brand new alternator.

 

So, 2nd new alternator went in, issue persists. It's plausible that I'm getting crap alternators from my local Auto Value store. Fuses and relays all check out fine. I'm about ready to drive this thing off a cliff.

 

This may help.

 

I appreciate the diagram. Unfortunately, in my 2004 R50, F38 in the driver-side footwell is left blank, both physically and in the fuse diagram on the back of the panel.

 

It looks like that may be a typo, and it should be F39.

 

 

I checked that when I was in there. That fuse is good. Is it plausible that my son, when installing the starter put the alternator cable on the wrong post of the starter? The two large terminals, we'll call A and B. I think he has the alternator connected to B, and the Battery cable to A. Is this correct? The car starts and runs, just doesn't charge, so I know that the battery being connected to terminal A is correct.

 

That doesn’t sound right. Isn’t one terminal on the starter the wire from the DME?

 

CAR IS FIXED. Thanks to the wiring diagram, my hunch was correct. Moved the alternator cable to the post for the battery cable. All problems are resolved. You guys are a treasure trove of knowledge. Now on to the next problem!