My '92 190E w/165,000 miles, just quit at a stop light, and would not start, even though the idiot lights were on and windows would go up and down. A jump got me started. Took battery to a parts store. They said it tested good, but was very low, took a 20 min quick charge. Took it to my mechanic who is methodical. He loosened and cleaned all the connections, even engine ground. He found part of the wiring harness routed too close to the exhaust manifold and had a toasty wire. He replaced a section of wire, soldered it, and rerouted the harness. He said alternator tested good UNTIL you put a load on it, like aux fan for a/c + headlights + interior fan...took it below 12V output. He says its the voltage regulator, which is inside the alternator. He doesn't know if it's a simple plug and replace or the soldered kind. Bosch W0120-485022. Looks original to car. Anyone know if it's a plug-in VR? Are we on the right track? Should we be looking at the year-old battery? Thanks for any light you can shine.

Sounds plausable...

that the 15 year old brushes are worn out...

not too pricy and if that's not your problem then they won't be next on the list of things to go wrong.

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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Voltage regulator can be removed from the alternator. IN a 2.3 you can even do it with the Alt still in the engine bay, just take the belt off and top bolt to swivel it out for more room. Takes about 30 minutes to do with all the right tools.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

Not necessary to remove belt or the alternator - two small screws secure the voltage regulator at the back of the alternator. A 10 minute job.

Attached a picture of the voltage reguator, trust this helps.

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