I think my Indy has gone over to the Dark Side.

I took mom's 2007 R320 CDI to the indy because the check engine light came on and it went into limp mode. Also, for the last couple months the oil level warning and the check coolant warning came up on the monitor. Both levels checked out just fine.

Indy calls back and says the batteries (starter and the Aux under the seat) are bad, which caused the alternator to go bad. The alternator tests with 15.8V output. Wants $1100 to fix it. He quoted $300 for a new alternator, then called back and said it was $450, then called back and said it was going to be $650. Estimate is now at $1450.

There doesn't seem to be a battery problem. The car starts perfectly normally, immediately, even in bitter cold weather.

Indy says the "modern" batteries fail differently than the old style, and when they do, the computer electronics are affected, and the alternator goes out.

I did research, the voltage regulator is on the alternator, its reasonably common for the VR to fail. Its a $70-$100 part.

I took the alternator to a local auto electrics shop and they quoted $150 to repair and test the alternator, including a new VR. The commutators are worn rough, he said they could be sanded smooth as the fix, plenty of copper meat left on them. They have it now, will be repaired in 24 hrs.

After the alternator BS story from Indy, I'm concerned the battery story is also BS and they are actually just fine.

Can anyone share what they know about batteries causing the alternator to fail, and causing the computer to throw odd codes?

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1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

AFAIK a lead acid battery is a lead acid battery and they've been failing the same way since they were invented in the century before last. That said, a bad one can shorten the life of an alternator, but that usually results in an alternator that puts out nothing.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

What were the codes?

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Jim

I guess codes wasn't the right word.

The display would show the oil level warning every time the car was driven.

It would also show coolant level warning most times.

Both levels are fine.

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

This makes it sound like you got some fault codes in there somewhere. Find out what they are and post them.

__________________
Jim

Can those code show if the batteries are bad?

I don't have any way to get them. Indy is pissed off at me for having them reinstall the old batteries.

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

Fault code information will go a long way to help us help you. A battery tester will tell you if the battery is bad or not. Codes can and will show up as low voltage. It should be easy enough to test the batteries with the proper tester.

__________________
Jim

Ok, thanks. When its back together I'll have them recheck the codes and write them down for me.

We do know it was charging over voltage.

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

Just a wild guess...older cars had an overvoltage relay that cut power to sensitive electronics when the charging system went wonky. On the newer cars, I think this function moved to the ECU. It could be that the high alternator output caused this function to engage, which in turn caused your alerts.