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Old 05-18-2002, 12:42 AM
Posts: n/a
Question Voltage regulator or alternator

Hello to all from a new member, and a new owner.

I bought a 1973 280C automatic yesterday. I drove it home to San Diego from Orange County, CA about 150 miles. I got home and parked. The very strong smell of sulfur was all over the place, burning my sinuses and eyes, etc. Opened the hood and the battery was boiling. It kept boiling for over an hour. I think I've got either an alternator or voltage regulator problem (and probably a ruined battery, not to mention all the electronics on board which may have been fried...)

Question: What is the procedure to replace the external voltage regulator? I don't have a service manual yet, so I'm in the dark somewhat. Should I remove the radiator to make more room to worK? Other than taking precautions not to short out the alternator, what would you guys do, or be thinking about to do this job?

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Old 05-18-2002, 01:25 AM
Registered User
Join Date: Apr 2000
Posts: 412
Sounds like overcharging of the battery due to a malfuntioning voltage regulator. The first thing would be to disconnect the battery. WEAR EYE PROTECTION! and face protection. This battery could be launched and very easily explode.
I would not condemn the regulator yet. The previous owner may have overfilled and overcharged a neglected battery so it would start when you came to purchase it.
i also believe the regulator is a Bosch that is a regulator-brush holder assembly that is part of the alternator. The assembly can easliy be replaced and is relatively inexpensive. I rplaced mine on my 190 by crawling under the car in the snow.
Good luck.
1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T
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Old 05-18-2002, 02:00 AM
MikeTangas's Avatar
Senior Member
Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
I'm not sure when they changed from an external to an internal regulator. My 1973 280SEL (W108 - actually a '72) has the external regulator bolted to the back side of the ECU. Take a look at the backside of the alternator, you should be able to tell if the regulator is internal.

If the alternator looks like this:

you should have an external regulator. Sorry I don't have a picture available of an internal regulator set-up.

Hope this helps.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

Non illegitemae carborundum.
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