83 240D Faulty alternator?

[Carrameow]

>Noticed starts get sluggish and then one day nothing. Battery dead. Replaced Voltage regulator/brush module on alternator. Replaced brushes practically gone.
>>Measured 12.5 VDC battery standing, 13.5VDC with car running,so I thought problem resolved. Believe voltage regulator/brushes to be only failure component in charging system/alternator since alternator ststor is just windings & not dynamic component.
>>> Getting ready to do complete diagnosis with schematic/replace alternator; however anyone have beforehand knowledge?

[jeffsr]

You need to check the system voltage with a load on the alternator. Turn on the AC, headlights, check the voltage at idle. Should be around 12.5-13. If below 12 then beware. Run it up to about 2000 RPM. If the voltage does not rise to over 12.5, then your alternator is dying. The slip rings on the rotor do wear out. New brushes can sometimes take a long time to seat on the slip rings. It's 17 years old. Time for retirement. BTW, the stator windings do fail. They can develop internal shorts and lose some of their capacity.

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Jeff Lawrence
1987 300e
1989 300e
1987 BMW 325

I don't know much about an 83 240D but if your car uses the "dreaded" ACC servo (the box with rubber hoses attached at the bottom and a bunch of vacuum hoses on top) it is possible that it is stuck and will not park when the key is turned off. This causes a slow drain on the battery because the servo motor never shuts off. The only fix is to replace the servo. I found my problem by removing the fuse that powers the clock. Then I removed fuses until there was no drain on the battery. So, if you determine that you alternator is good, you might give this a try. I hope this helps.

Be kind, I am a first time poster to this forum.

[Benzmac]

The 83 doesn't have a servo.

The way we check alternator output is by measuring the Amperage output. At home you may not have an ammeter, so you will have to rely on the voltage check. The problem is that a generator can easily put out 13volts with 2 amps. You need to have it checked with a good load capable tester.

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM