My battery light has been flickering for about a week. It's also been really cold here lately. Some of the mornings my car started slow like a bad battery. This morning I went out to start and got couple of chugs and then nothing when starting. I jumped it off my Suburban and it started fine. Drove it to the Advance auto and they tested it. At first it looked ok, and then I tried to start it again but got nothing. Then he checked it and it showed dead. I bought a new battery and it started up great. My battery light is still flickering when idling like it was before. I thought he checked the alternator while I was at Advance, but I'm not sure. Now I'm wondering if I bought a battery when I might be needing an alternator. I'm no expert so I forget what to look out for sometimes. Am I just being paranoid here?

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"Gerwalt" 1984 - 300TD

Could very well be your battery was good and your alternator was not charging. I hope you kept the old battery.

Here's my thread replacing the alternator.

Is this a good Ebay alternator for W123?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Check the voltage regulator for worn brushes before replacing the alternator, an easy two screw affair.

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83 SD

84 CD

I did not keep the old battery. I thought that he did check the alternator, but after I got to work I started wondering. He did mention 14.5V at some point after it was running. Does that mean he checked the alternator?

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"Gerwalt" 1984 - 300TD

Sounds like a charging system problem. Put a voltmeter on the battery before starting then after it is started and running at about 2000 rpm. Should be 12.5 to 13 with the key off and a solid 13.8+ at 2000rpm. Anything less and there is a problem. Also check all ground cables and straps.

14.5 volts is good charging voltage. If the batt light was flickering it could be intermittently charging. Definitely change the regulator first and see if that solves the problem.

Also clean all elec connections including the 3 pin connector.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

A common thing for faulty voltage reg's to do is to just totally shut off at idle. it is 8 bucks and two screws and really only about 10 minutes of work with a flat head screw driver.

It's also entirely possible that the light is something to do with my cluster. I can't rule that out because my dash loses it's ground intermittently and all the lights go nuts.

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"Gerwalt" 1984 - 300TD

x2

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

also could be loose belt.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I think the alternator bit the dust tonight. I was driving home and all the electrical stuff faded out. No headlights or anything. vstech told me to charge my (new) battery slowly in order to keep from damaging it further. My charger has a 2a and 10a setting, which would be better in this case?

Hoping to pick up another alternator tomorrow or Thursday.

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"Gerwalt" 1984 - 300TD

10A until it won't go any further (ammeter on the charger zeroes) and then 2A for a few more hours just to trickle that last little bit in; that's how I do mine anyway.

Check the voltage regulator before you throw money at an alternator. Cheap, easy, and likely. Just pull it out and look at it. If the brushes are worn down, replace it.

In response to funola, I'm not familiar with many parts places that let you keep the old battery -- at least not without an expensive core charge. Around here it's one-for-one exchange and even if you let them keep their core money, they do their best to persuade you that you NEED to bring that old one back.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Just an FYI here. A new alternator/voltage regulator, can be burned out in short order by a battery too weak to be renewed by the new alternator/voltage regulator. It happened to me that way, and it took replacing them both simultaneously to solve the problem.

yup that's a good reason to fully charge a battery before you attach it to the car. might even be a good idea to take it to a testing place of your choosing to verify it's fully charged and working properly before you use it!

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Who do you trust to test them? I've had Advance test one for me and they told me it was not only in good condition (6 years old) but the CCA number they returned to me on the printout was higher than what the battery was rated for when it was new.

It died a month and a half later. About the only "test" I trust is how long it takes the charger to pull it down to 0 amps, and whether it actually manages to do so or if it "stalls" at half an amp or an amp. Usually that means it's done for.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL