All-

Started on Saturday. took family to the mountains and parked the car, went back to the car. Dead. Called MB Roadside assistance and they sent someone out to jump the car. Car Started went to advance and bought new battery as old battery tested 1 dead cell.

Wednesday on way into the work. Radio stopped working, climate control went dead and when I got to work to park the car. Car would not start. Waited til lunch and car would now start not the same vigor (weak battery).

Tried to restart, would turn over but barely. Seems like a voltage regulator/Alternator issue. but do not want to start "just replacing parts". Any one seen this before?

Thanks

Advance can test your battery and charging system. FREE.

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92 300D 2.5L OM602 OBK #59

Do I have to take all the goodies out like the alternator

Simple test if you have a volt-meter (DC).

Car off, battery should read over 12vdc.

Start the car, accessories off idling it should start to climb to ~13vdc on the original alternator, between 13vdc and 14.5 is fine.

Turn on the headlamps and heater, will likely drop a little but still maintain over 12.5vdc (again 13-14.5vdc is better, but the original alt is weak at idle). Rev to 1200rpm and voltage should rise back above 13vdc.

It is a normal failure mode for the brushes on the regulator to fail, then you get no charge (sometimes intermittant for a short time) with no alternator-warning light. The regulator comes off with two phillips screws, an easy replacement.

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Gone to the dark side

- Jeff

Thanks Jeff, I certainly hope that is it. I'll keep you posted.

No red alternator out light on dash? Check voltages as suggested already. Also make sure the glow plugs are shutting down after their cycle. Should be able to tell this by roof light brightening up when the glow plug relay drops out. Also listen for the audiable noise of the contacts opening as well.

No red alt on the Dash. Had a mechanic tell me once this was the most useless indicator as they are not accruate. I suspect Brushes alt as MB has always displayed weird/bizarre behaviour when voltage gets flakey. I do ahve a DC meter so we will give that a ride.

The alt light is accurate, ... if you lose the belt. Pretty much comes on if the battery voltage is higher than the charging output, if the diodes don't all fail and the brushes don't lose contact.

Unfortunately the most common failure mode in my experience is worn brushes, which my first 124 experienced when it was only about 4years old, ... in a snowstorm, on Christmas Eve, late, with the entire family and gifts on-board, in the middle of nowhere, not what you'd expect from a Mercedes.

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Gone to the dark side

- Jeff

Well, Went through the test. Battery is at 12 volts. Car running at 1500 rpm 11.8 V with Headlight blower on. ordered new voltage reg from advance - $36

Mine was only putting out ~ 12V measured at the battery posts on a cool day (50*???) and the car warmed up after a several mile drive. Monkey at parts store was sure it was the alternator. I unplugged the glow plugs at the control box & voltage went up to where it should be ~ 14V. I'm going to the yard for GP relay.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Thought I would post a follow-up. Voltage reg did the trick the old one was worn to the nub. $36 and 15 minutes we are good to go.

Sweet. Glad to read it's fixed and went well.

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92 300D 2.5L OM602 OBK #59