HELP! I have looked everywhere in the postings and cannot find an answer to the problem.

It all started when the car was in the body shop being de-rusted and re-painted. When I got the car back, I had the alternator/water pump belt squealing. A couple of days later, the belt broke on a lonely highway just after midnight. I had the car towed in and replaced the belt.

Now when I am driving the car, the seatbelt warning light will come on once to four times in my 50 minute drive to work. At night, the headlights flare up. Sometimes they stay bright (up to 50% brighter) for more than 10 minutes, other times they just pulse bright and then go dim. When the lights surge, the defroster fan kicks into hyper-drive, and if I am using the wipers, they double in speed. This surge in the other electrical devices seems to have no correlation to the seatbelt warning light. It will come on before, during, or after the surge in power.

I have had the alternator bench tested, and it checked out fine under a load. I have checked out the seatbelt contacts and switches, they are okay according to the meter. The battery is old, but not that old. However, could this cause the surge I am seeing, if the battery has problems, will it cause the alternator / voltage regulator to kick into turbo to compensate for the battery's problems?

Any assistance or suggestions would be appreciated.
Thanks, William

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76 240D - 545K miles
78 300D - ?K miles

Connect a voltmeter to the battery and monitor voltage when this happens. Sound like a possible intermittent voltage regulator. If voltage exceeds about 15v this indicates that the reg is not working properly. 17.5 volts is critical.

Thanks, will give it a try this evening.
Will let you know.
William

I had a somewhat similar problem with a 280E. It turned out to be water and corrosion under the main fuse block. It made the electrical system do totally bizarre and random things.

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Chuck Taylor
Falls Church VA

Thanks, Corky... checked the voltage this morning. It held steady at 13.8V. I hooked the long leads to the meter and set it on the dash, then took a drive. The meter stayed pretty constant for a while at 14.2, then spiked at 15.5 and briefly hit 17.53 a couple of times.

I guess I need a new alternator / regulator.
Are these together in the alternator casing or separate? I have never bothered to look or check a diagram. Any idea on price? Can it be rebuilt locally, cheaper or better than aftermarket rebuilt?

Note to CTaylor... fuse box is clear of moisture and corrosion... checked that already... thanks for the info anyway

The voltage regulator brush pack can be replaced without removing the alternator. Two screws hold it on. They are very cheap. Should be less than $30. I would remove yours and feel the shape of the commutator. Its almost worth the gamble of that alternator to just replace the regulator. The problem will be that if the armature is too unround and grooved it will eat the brushes in no time as they will have so much more tention than the old ones.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks stevebfl,
I will check the unit in the morning. If necessary, I will have to replace alternator also.... close examination will tell....

Is the original unit a BOSCH or other design? I have not looked. I want to put an original type back on, if necessary.

William

Thanks guys,
Replaced the Regulator and everything went back to normal. (part was $39.77 total)

The alternator is in great shape, should get a few hundred-thousand more miles out of her.

Thanks again,

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William
76 240D - 545K miles
78 300D - 200K+ miles

WmHarlow,

Only 545K miles and already having trouble with the alternator? Can't get anything that'll last 'til the water gets hot these days.

Good job,

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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Those cheap German alternators!
Only 545,000 miles and already giving trouble.
I'll bet the radiator will go next.


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Bill Wood - Webmaster
MercedesShop.com, LLC

Lousy Plastic German radiators...

Larry

Please.....
Don't jinx me..... or my radiator...
Having it flushed tomorrow... would hate to think the scale is the only thing holding it together.

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William
76 240D - 545K miles
78 300D - 200K+ miles