Battery Light on DEAD ALTERNATOR

**M5XTu** · 11-21-2018, 10:00 AM

I haven’t driven my 01 540/6 much since I bought another car. I’ve only put 79 miles in the last 8 weeks. Car only has 129,101 miles on the clock. I decided to drive her last Friday and battery light came on after about 2 miles of driving.

Went to AutoZone to have battery checked. They said good battery but weak.

Brought car home, disconnected negative cable and put it on a 2AMP charge for 2 days. I started out with 11.83VDC and ended with 12.47VDC. Reconnected the negative cable, started car and battery light stayed on.

I checked the voltage at battery while on idle and I show 11.92VDC.

Looks like I need to replace this water-cooled alternator.

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**JimLev** · 11-21-2018, 10:25 AM

Early Xmas present for your car, good luck.

**dannyzabolotny** · 11-21-2018, 12:26 PM

Yep, sounds like a bad alternator. It’s pretty straightforward to replace— you just disconnect the battery, drain the cooling system, remove the fan shroud and serpentine belt, and remove the 10mm bolts along with the big 17mm bolt on the alternator. Last time I did one it took less than 2 hours start to finish.

**demetk** · 11-21-2018, 10:15 PM

Maybe it's just the voltage regulator?

**dannyzabolotny** · 11-22-2018, 12:06 AM

Originally Posted by demetk

Maybe it's just the voltage regulator?

Even if it was, pretty sure that's internal on the water-cooled alternators... no easy way to rebuild those on your own as far as I can tell.

**JimLev** · 11-22-2018, 12:55 AM

The regulator is replaceable but good luck finding one that actually works. I bought 2 new ones, neither worked. Sticker on the box said made in Mexico but under the sticker was China.

**demetk** · 11-22-2018, 08:05 AM

Originally Posted by dannyzabolotny

Even if it was, pretty sure that's internal on the water-cooled alternators... no easy way to rebuild those on your own as far as I can tell.

Which models came with the water cooled alternator? On my 01 touring I see air ducts connected to it. Is the water cooled option supposed to make the alternator last longer?

**JimLev** · 11-22-2018, 08:49 AM

The V8 tu engines, 99 to 03 had the water cooled alts. They are support to be quieter as they have no external fan on them for cooling or brushes to wear out.
The other alts that use an air duct for cooling can get packed with leaves, cig butts, etc. They should be cleaned out so they don't overheat.

**M5XTu** · 11-23-2018, 10:00 AM

I have not started this fix yet. I just ordered the O-ring and will pick up today. Once I take the old alternator out, I will have it tested to see what has gone bad.

There is a rebuild kit on fleabay for those who want to rebuild theirs. I, however, have 2 extra units in my garage.

https://rover.ebay.com/rover/0/0/0?m...2F300919890994

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**JimLev** · 11-23-2018, 10:23 AM

That rebuild kit price looks good, all the parts you need.
If anyone buys this please report back if it works.

I've got a spare alt from the junkyard that I picked up years ago.

M5XTu, how are you going to get your's tested? All the chain autoparts stores I took my old alt to couldn't mount it in their tester and didn't have the correct cable.

**M5XTu** · 11-23-2018, 10:27 AM

Originally Posted by JimLev

That rebuild kit price looks good, all the parts you need.
If anyone buys this please report back if it works.

I've got a spare alt from the junkyard that I picked up years ago.

M5XTu, how are you going to get your's tested? All the chain autoparts stores I took my old alt to couldn't mount it in their tester and didn't have the correct cable.

I had no clue they couldn’t test it. I will call before I take it in.

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