I have a 1980 300SD (116chassis). The battery does not charge. I have a new battery and installed a remanufactured alternator, and the problem persists. I have 11.8v at the battery terminals, and with the engine running, if I disconnect the battery terminals and check voltage at the battery cables, I get 2.4v. Any ideas? Does anyone have a charging system circuit diagram they can send? is there an external voltage regulator that may be faulty? Thanks.

First of all have the new alternator bench tested. The odds of getting a bad reconditioned unit are higher than they should be. If your replacement alternator came from a chain type parts store especially.

NEVER disconnect the battery cables with the engine running, it blows the voltage regulator.

* Disconnect the battery.
* Test the alternator harness for continuity.

Links with all you need to lern for correct charging circuit diagnosis.

Automotive repair training book on line, you can download it.
http://www.tpub.com/content/construction/14273/
and
http://www.tpub.com/automotive.htm

http://www.carbibles.com/



Have a great day.

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1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

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Is your belt SUPER tight? I couldn't figure out what the problem was until I messed around with the tension of the belt. If it is the slightest bit loose on these cars, they will not charge. Check it out. I also know that bad grounds might do it. Wire brush the connections under the battery box and the connection on the transmission. Those are both trouble spots.

Good luck!

If your charging light does not come on whey you first Turn you key on the bulb may be burned out.
You need the bulb circuit to be complete with a working bulb or your Alternator will not charge.

Pull out the Connector Plug at the Alternator. There is 2 large slots that are the same size in the connector and behind it are 2 fat red wires. You should get Battery Voltage at those 2 wires all the time; key on or key off.
There is 1 smaller slot with a much thinner wire behind it; on my 123 it is a Blue Wire. This is the wire that goes to the Chargeing Light.
With the Key Off there should be no voltage there. With the Key on you should get slightly less than Battery Voltage. If there is no Voltage with the key on you have a problem some where in that circuit and your alternator will not charge.

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84 300D, 82 Volvo 244Gl Diesel