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1999 ML 430
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419 Posts
Discussion Starter · #1 ·
OK, the ML left me sitting for the first time last week. Wouldn't start, only got a click-click. I said bad things to She Who Must Be Obeyed (SWMBO) about leaving stuff on, charged the battery and it started. Ran a few errands without shutting it off and brought it home and put it on the charger overnight. Wouldn't start next morning so had it towed to the dealer.

They came back wanting a couple of grand because it needed a new batt and alternator. I argued with them and told them I could take the alternator out and it would still start, so they needed to look further. They called back and said it needed a new battery and the alternator was "marginal" but just the battery would get it back on the road. So, I'm only about $500 poorer rather than $2000, but I need some info on the alternator.

ML 430 alternators are EXPENSIVE! How does one measure "marginal?" My experience with alternators tells me that they work or they don't. Is there a marginal state of alternator? How do you measure "marginal?" What are common problems with 430 alternators? I live in a cold climate that is hard on electrical systems, so I need the electrical system to be sound. You don't want to be around if SWMBO goes out to that car after work and it won't start!
 

· Registered
1999 Ml430
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351 Posts
One word: Alaska.. thats like shipping something to Russia. Everything you looking at about this car will be double for you. OEM alternator is a bit more then $1000 and the batter is less then half what you paid.
Don't you have some relatives who could help you out and order the stuff for you and then us US mail to ship it to you.
 

· Registered
1999 ML 430
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419 Posts
Discussion Starter · #3 ·
Oh, I know how to get stuff to Alaska.

I have an Alaska Marine Lines account so I can get the "free shipping," at least to the Seattle address; nobody ships free to Alaska. You know you've lived in Alaska too long when you can have something shipped to: Art and Juno/Anchorage, AK C/O Alaska Marine Lines, 15 somehting Marginal Way, Seattle.

There are plenty of freight forwarders and combiners. It will never be cheap, but I can avoid extortion. There are no words for how much I hate businesses who will only ship UPS 2nd Day Air or FedEx to Alaska! Half the time the freight is all together in the belly of the Alaska Airlines plane; the only thing that changes is the price.

My issue is whether I need one at all and I don't know how to make that determination.
 

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Dallas, Texas
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13,414 Posts
It's not how you measure marginal. It's how you measure good. 14.1V is good, 13.6V is lowest it can get. Test at 2000 rpm. First with all stuff off then start adding load. Headlights, blower on high, rear window defogger, heated seats, wipers.
 

· Registered
1999 ML 430
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419 Posts
Discussion Starter · #5 ·
Where do I measure the output voltage?

The damned thing is so complicated, I don't know where all the wires go. Ground to chassis and hot on the positive battery terminal? Output wire on the alternator? Part of me thinks it was just the "stealer" thinking I was one of those MB owners with more money than sense, but if the alternator is going bad, I'd like to replace it with at least a reman before it fails one cold morning. I've just never had a "half-bad" alternator; they worked or they didn't. Thanks for the help!
 

· Registered
99 ML320, 04 E500
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97 Posts
Connecting to the battery is fine. Clamp the wires down and put the voltmeter display on your windshield and watch the voltage at idle and rev. You should see the voltage increase when you rev.

Alternators can slowly weaken (faulty voltage regulators or just a dying alternator) or if you're driving a lot of short in-city trips, the alternator never really has a chance to recharge the battery.
 

· Registered
Dallas, Texas
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13,414 Posts
The damned thing is so complicated, I don't know where all the wires go. Ground to chassis and hot on the positive battery terminal? Output wire on the alternator? Part of me thinks it was just the "stealer" thinking I was one of those MB owners with more money than sense, but if the alternator is going bad, I'd like to replace it with at least a reman before it fails one cold morning. I've just never had a "half-bad" alternator; they worked or they didn't. Thanks for the help!
It does not matter where you check it. At the battery, cigarette lighter, OBDII socket or fuse box. In properly working system voltage will be same everywhere.

"Complicated" starts if there is a drop of more then 0.1V

Alternator has six diodes that change its AC output into DC needed in the car. If one of them starts to leak you will have half ass alternator with output of about 12.6V. Enough to keep car running but not enough to maintain battery.
 
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