In my workshop this week...

[Uncle Benz]

I’ll start by apologising, I didn’t take any photos...
I had the pleasure of a very tidy S203 estate with an m271 engine this week. 58k on her, and very well kept. The owner is the father of one of my long time customers. The car came to me with some history and work carried out elsewhere. There must have been some battery issues, probably brought on by lockdown. The battery had been replaced, but an occasional red battery symbol in the cluster led to a reconditioned alternator being fitted. The battery warning persisted, but now accompanied by abs faults, auto lights offline and gearbox sticking in low gear. A key off/on cycle would clear the problem. The car had additionally had the battery earth cable replaced, to no avail. The owner came to me asking for the front SAM to be replaced. I was immediately cautious. I can count the number of front SAM’s I have replaced on the fingers of one hand. Rear SAM’s are another story. I’d need the fingers of three pairs of hands to count them...
I had a known good secondhand front SAM on the shelf, so to humour the customer I tried that first. Exactly the same. I then scoped the battery voltage, and was a little surprised to see the occasional spike of 19 volts occurring! The breaker up the road had a 2009 CLC just in with rear end damage. I grabbed the alternator from it to test, and the fault was immediately solved. Conclusion? Reconditioned Bosch alternator was the problem. It wasn’t a Mercedes service exchange unit, which is my default choice with these. I’m sure it was an isolated case, but be aware, these smart charge systems can be finicky. If you scope the battery now you can see the alternator has a “soft start”. Battery voltage drops to 11v cranking, rising to 12.3v as the engine starts. Over the next 5 seconds it climbs to 13.8v and sits there. If you apply load by switching on lights, wipers, blower, you see it immediately respond. The faulty alternator spiked to 19v on engine start, then rapidly returned to 13.8-14v, but the initial spike caused some control units to crash, and plenty of faults to be logged. It’s a miracle further damage hadn’t been caused!
The owner collected the car this morning. He insisted that I didn’t start the car before he arrived. He wanted to see with his own eyes it was actually fixed.

 

[robin.large]

Good shout. Some stuff is ok for buying readily available anywhere stuff. Other parts need more care!
I'll bear this in in mind!

Sent from my ONEPLUS A5010 using Tapatalk

 

[Uncle Benz]

A small thing to note, both Bosch and Valeo units were fitted at the factory. In my experience stick to the brand it originally came with. If you ask Mercedes parts for an alternator, one of the first things they will tell you from their screen is whether it came originally with a Bosch or a Valeo. I think they know something...

 

[sonic]

A most interesting report, thanks.

 

[davemercedes]

+1 Very interesting thanks!
Seems so simple - but if it was, nobody would ever have a problem!

 

[Uncle Benz]

Yeah. A bit of an Occam’s razor. Everyone had assumed because the alternator had been replaced that the fault must lie elsewhere. Assumption, The mother of all f-ups.

 

[MinionBob]

Nice write up.

If I were to call up Merc and ask for an alternator, do you have to specifically ask for a recon unit, or will this be the default option given to the (member of the public) customer?

 

[Uncle Benz]

Nice write up.

If I were to call up Merc and ask for an alternator, do you have to specifically ask for a recon unit, or will this be the default option given to the (member of the public) customer?

Depends on the dealer I think. Certainly with things like SAM units they won’t immediately mention that service exchange units are available. Only when pressed do they concede that they are. Often they’ll tell you they have a new unit in stock but a cheaper exchange one will be a few days to arrive. Naughty really.

 

[davemercedes]

Very naughty indeed. When I worked in the sharp end i ran a Parts Area distributorship and had excellent contacts with Lucas. I found I could send used units - everything from fuel injection (the so-called “metering pumps” - (bear in mind that petrol injection was still very new back then and retail was way over £100 for one of these in the late 1960’s). They would rebuild anything from alternators to starter motors fully overhauled/rebuilt.

The lead time was a little high - I think simply because they repaired the entire batch - whether it was 3 or 30 units but the rebuild quality was incredibly good - I never had a single failure (but I did with official exchange stuff (B90 in those days).

Over the years I lost a lot of contacts and of course most of those guys will, like me , be retired now and don’t have to source material like that anyway. Sad really - a slice of the engineers we had in the “good old days” have gone! The industry was surprisingly honest too - many a time I had serious help from someone I’d never met before - back then it was mostly a genuine brotherhood.

 

[davemercedes]

bump

 

[MinionBob]

Depends on the dealer I think. Certainly with things like SAM units they won’t immediately mention that service exchange units are available. Only when pressed do they concede that they are. Often they’ll tell you they have a new unit in stock but a cheaper exchange one will be a few days to arrive. Naughty really.

Thanks. Your words echo my thoughts exactly abut how they typically sell you a remfrd part - i.e. only available when you ask for it.

There is a Merc website for rmfrd parts, never used it...

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