Jerry From LA wrote:
The screeching noise in your starter is the starter drive spring. It's on its last legs. find a good rebuild shop near you (I'm in the LA area so there's one 1/2 mile from me). Have them rebuild your core. Good to have a nice fresh starter for the winter.
Yep, I have a shop near me that does really good work; unfortunately they have like a 6 month lead time. It's one dude, working in his basement, with piles and piles of generators, alternators, and motors around him.
Well, I have a spare starter that came with my parts car. I tested it with jumper cables and a screwdriver, and it worked, so I decided to try swapping it tonight...
But first, I decided to check over the charging system to make sure nothing else could be causing the low voltage issues before dumping $$$ on a new alternator.
The alternator was marked "AL-80X, Remanufactured by Bosch" so it was an original type 55 amp unit, and had been replaced at some point. With the engine at idle, I got 14.1 volts at the alternator. Huh. That seems...perfectly fine. With the engine off, I checked resistance between the positive wires leading from the alternator to the battery- about two-tenths of an ohm. The connections on the alternator were clean. I checked the alternator belt tension, and it was a bit floppy- about 1/2" of slack when I pressed on it. So I tightened the belt. Then I checked the resistance on the negative side of the circuit and got...
15 ohms.
Huh? Yeah- double checked it, triple checked it, checked my meter, then checked again.
'15. Freaking. Ohms.
15 ohms is about 14 and half ohms too many, in my engineering judgement, for a negative return path. So, the cable from the battery to the carbody was removed, checked for resistance, cleaned, coated with a film of dielectric grease, and reinstalled. Ditto with the engine to carbody braided cable- which required jacking the driver's side to get to. I cleaned all the battery connections and made sure everything was tight, and then re-measured the resistance.
0.2 Ohms. Phew.
Next up- trying the presumably-good used starter. I had to jack up the other side of the car to get to that, and found that Mercedes, in good German fashion, had done a couple of things just a little different than every other automaker:
a) The starter was attached to the bellhousing with two bolts, but they were Allen-head bolts. The top-most one was inaccessible from the top of the engine and damn near inaccessible from the bottom. I had to get an Allen socket, put it through a same-sized Gear Wrench (ratcheting wrench), and use that to loosen the bolt. My ratchet would not fit.
b) In order to extricate the starter from the car, the car had to be jacked in the air (which it already was), and the front wheels cranked all the way to the right in order to get the idler arm and tie rod out of the way for the starter to pass between them , the crossmember, and the exhaust pipe. Barely. I'm sure this was "As Designed", and it probably tells you to do just this in the MB repair manual. And then drink several Warsteiners.
After a 15 minute diversion whereby a Craigslist guy came over to buy a 351 Cleveland engine from me, I got back to the reassembly of the Merc, which thankfully really was "The Reverse of Removal". The starter worked as it should, the alternator charged, and order (for now) seems to be restored to the Krautbeaterwagen Universe.