Another thread and another car to take a break from some FPR/OVP issues I have with another 300E I drive that some of you were good enough to try and steer me through. That still unresolved issue I had to leave for a while rather than shoot the bug*er.

That said, I'm onto car number two and first order of business was removing the alternator which isn't charging a good battery and is only according to the seller a year old. The car has 190K stored indoors most of the time. Wiring is mint and barely any rust anywhere.

Car starts great with a boost - red charging light always on. Good battery which eventually drains since there's no charge coming back. Alternator
turns fine, no noise, bearings are good but it isn't producing any juice.

Hoping once I fix it will go back in easy. Assume the worst will be getting the belt back on the pulley. I'm going at all this w/o a manual but lots of domestic car experience and I know there's a tensioner to loosen but I couldn't find it or how to access with fan blades, shroud and rad in place.

Questions. Reading through some old threads I've seen some discussion about repairing the alternator myself. They're going to ding me for $100 plus minimum to rebuild, closer to $200 for a rebuild from a autoparts dealer. If I can save that by doing what is suggested in other threads that would be great. Being that it is only a year old, I can't figure out why it isn't generating. Saw an article that mentioned a VR/brushes cleanup that might be the problem? It's a 'valeo' regulator which looks new. Based on my alternator knowhow I wasn't aware a VR could be what makes an alternator fail. Thought a VR only handled the charge once an alternator produced a charge as opposed to being the cause for no charge at all.

But the nut on the negative (small) terminal bolt of the alternator is impossible to loosen. I ended up snipping the wire close which is easy to solder a terminal end back onto once repaired and getting a good crack at it off the car seems to make sense. I soaked it with penetrating oil but it is on tight enough to spin the bolt it's frozen onto and since there's nothing to grab to stop the bolt from spinning I'm wondering how to get it off. There is a nut below the seized nut and terminal end but it's buried too deep to grab with anything, there's no way to jam it from turning since the black plastic insulator that surrounds the bolt would break trying to jam anything in the keep it from turning. It's on so tight I'm thinking it must have 'cooked' itself on - that may be the problem.

That alone may spell rebuilder. If that terminal bolt spins around is it not breaking the contact or wire it's attached to inside?

benzborg -

The stock Bosch 70A alternator that would have come with a 1988 300E isn't strong enough really to power that car. Which is why MB quickly went to the new 80A alternator (in 1990 I think). Not only does it make more power overall, the key is that the 80A version makes considerably more power at idle speed. The 70A needs higher (i.e. driving) speeds to make anywhere near its rated load.

So...if the '88 300E is a keeper, you may want to simply upgrade the alternator while you are at it. You might be able to fix the 70A, but it will probably cause headaches for you down the road. If you are going to get in there and spend time and effort on it, I would strongly advise getting the 80A.

I made a detailed post about it, including removal instructions, see below. Also note MB DOC's statement re: under-powered alternator.

http://www.peachparts.com/shopforum/showthread.php?p=534174

Good luck!

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

Personally- my 86' is cranking along fine with it's 70A alternator.

I'd replace the regulator/brush pack with a new Bosch. These alternators are pretty durable. But if you want an upgrade and are willing to make a new harness to go up to the battery- go with the 143A which will bolt right in. Those bring $65-100 used, plus a new regulator $25 and then plan another $40 for wiring.
If you're going to replace it- I'd go only with a rebuilt bosch. I wouldn't mess with any alternator shops. Factory sells them with a longer warrentee I believe. Depending on your local dealership- they can be same price or less than on-line.



Michael

Are you guys in Europe I wonder? The prices listed above might buy a carwash in Canada. I'm hitting the phonebook to the alternator shops to try and get close to the prices you list. The MBZ dealership for example lists the VR at $130. How can that even be when you're talking $25 above is what I'd like to know. I know dealers are historically expensive but even "regular" parts shops for anything Benz around here are banditos. Since it's apparently been replaced a year ago I keep thinking it must be something I could repair w/o a full replacement. Getting someone to only charge for the "easy" possibility instead of charging the full replacement price is the challenge. Most shops today want the flat rate for "rebuild" no matter what's wrong. Oh well - might be time to find a scrap alternator and crash course myself on how they rebuild them front to back. I'm one of those old hacks that only sees value in driving and enjoying old cars if it remains dirt cheap to fix them. Letting the wallet do the work seems to be against the purpose of it all.

thanks for both replies guys - all good info to consider and help me get'er done.

"Fixed" is a word I currently envy. This is already one of those jobs that has the hands minced and aching. At least the engine will be cold when I put the bu*ger back in. Since this unit doesn't have the plug in harness I'm wondering if it isn't the 80 amp. There's no brand labels or marks to say what it is, only the VR has the name. One way or another I'll have it done today.

Thanks for that link.

Does your existing alternator have two mounting bolts or a female harness plug attached to it? If it is just the two mounting bolts (one large, one smaller), then it could be the 80A AL66X already. Here is some more info on it from a solid source -

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

Ended up paying the price to have it rebuilt local - a guy who I've dealt with before charged me $120 with a new VR thrown in. It is an 80A and the stator was munged beyond belief, I mean *meltdown*. The seller must have tossed me the "new last year" story because I've not seen such a mess inside an alternator before. Makes me wonder what other electrical issues the car may have.

Oh well, we'll get it in this morning and go from there.

Thanks for the help guys.

Good to hear you have the upgraded one. Particularly for winter, which is where you can get into problems with the earlier one. With defogger on, blower fan on, defroster...mix that with lots of idling in slow winter traffic and you can overwhelm the 70A pretty easily.

$120 for a rebuilt alternator is a pretty good deal. I paid $350ish for a new 80A about 5 years ago.

You should be able to install it without removing the serpentine belt.

Good luck!

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

Yep,

Like I said originally (or meant to). These alternators are pretty reliable so I'd get a used 143A and a new regulator and be out less than paying a shop to rebuild. I feel more comfortable with that than a shop rebuilt. Just me.

Disadvantage with the big alternator- it does have a larger polar moment of inertia and obviously more fanbelt load when it's loaded hard.

Michael