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  #1  
Old 04-19-2002, 10:26 AM
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battery dash light stays while engine is running (300SD)

On my 1983 300SD the battery dash light stays on while I am driving but goes out when the engine is turned off. The brake sensor and emergency brake lights stay on with it at first then go out while the battery light stays on while I am driving. I checked the v-belts and they are tight. Car starts ok and the battery seems to be charging.The following parts have been replaced:

New alternator/voltage regulator is 3 months old.
Starter/solenoid is 2 years old.
$100 battery is 1 year old.
All of the glow plugs are 2 years old.

Could this be a relay, wire or fuse problem? I did a search on this forum but could not find an exact match to my situation.

Thanks for the help!

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

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  #2  
Old 04-19-2002, 11:23 AM
Fimum Fit
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Diode failure in Bosch regulators can cause the light to glow

even though the alternator is charging. The first car I owned with an alternator rather than a generator (many years ago) was a '66 Porsche 911, and I ran it that way for 4 years and 50,000 miles before I became aware that it wasn't supposed to be that way (by reading Porsche Panorama).

If you take a car with a really dead battery and then jump start it and expect the alterator to fully charge the battery while operating all the other electical stuff, that can sometimes ruin diodes thus.
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  #3  
Old 04-19-2002, 11:38 AM
moedip
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To isolate problem - Get a digital multimeter and check the voltage at the battery with the car running - it should be 13.6-14.7 volts - if it is lower - suspect alternator or brush assembly - if it is 13.6-14.7 - suspect circuitry problem - not charging problem
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  #4  
Old 04-19-2002, 05:16 PM
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About a year ago I had a situation where I went through three alternators in 6 months (Thank God for warranties). I turned out that the battery plates had shorted and the alternators just worked their little selves to death. If your alternator is putting out between 13.5 and 17 volts, try a fresh battery.
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  #5  
Old 04-19-2002, 05:33 PM
moedip
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If the battery voltage is MINIMUM 12.4 volts with the ignition off - the battery should be fine (a real healthy battery will be about 12.75-12.90V. If there is a shorted or open cell the voltage will be MAXIMUM 11.80 volts or less. I just went through this exercise on two cars this winter (3 alternators and 2 batteries later!)If I would have checked the static voltage on the battery first - I would have seen it was at 11.56 with a shorted cell that killed my alternator and burned out the wire harness from alternator to the battery. Before you wholesale try parts - try my voltage checks - they will save you time and money.
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  #6  
Old 04-22-2002, 12:43 PM
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Thanks for the replys!

Just did a multi-meter check at the battery:

12.4 volts with engine off
11.8 volts with engine running

Could this be a brush (regulator) or altenator? "USA Muffler" just did a new one for me on 2/22/02 for a mere $450.00!!! (I was on the road and did not have my tools !! Damn!!! They said it was a Bosch altenator ($250.00) but Car-Quest delivered it to them so I do not think it is a Bosh. The regulator looks new also and came with it. I want to call them but what should I do or say to them, it is under warranty.
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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

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  #7  
Old 04-22-2002, 01:44 PM
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NOW THE CAR WILL NOT START!



OK now the car will not start! Before lunch voltage raadings were as posted above. Upon returning to work I took the following voltage raadings:

11.5 volts with engine running, 10.5 volts with the a/c going and 10.5 volts with the engine off.

Now the car will not start.
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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

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  #8  
Old 04-22-2002, 01:49 PM
moedip
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If they are both under warranty - get them to check them - you definately have no output from the alternator circuit. Before you condemn them though - I had one case where the lead from the alternator to the battery was burnt open. Check the voltage output at the back of the alternator first - if it is 14V or so - then follow the wire back to the battery to find the open. If it is still 11.8V at the alternator then have them check the reg. and alt. under warranty.
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  #9  
Old 04-22-2002, 01:52 PM
moedip
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Of course it won't start - you drained the battery to below 12 volts. Charge the battery up and get the alternator circuit fixed. A little advice - if your alternator is dead - all you have to rely on is a discharging battery with no recharging to replenish current. If you want to drive the car to the repair shop - fully charge the battery first and DON'T USE ANY ELECRICAL ACCESSORIES AS IT WILL DRAIN THE BATTERY QUICKLY AND LEAVE YOU STRANDED.
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  #10  
Old 04-22-2002, 03:34 PM
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James L.,

If your measurements showed the Voltage across the battery was lower with the engine running, you either have a short in one of the accessories you had running or you have a defective alternator, or both. You may have damaged the battery as well.

I think you should have the alternator checked out first, including the Voltage regulator, and the battery. It has been my experience that shops often rebuild alternators and fail to do a real electrical performance check to look for bad diodes and weak stator insulation. Consequently you can get a poor performing alternator from the dealer (I have) and get sent way off track troubleshooting the problem because you just can not believe the "new" alternator could be the problem.

Good luck, Jim
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1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
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1991 350SD (176,560 miles, weakest Benz I have owned),
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  #11  
Old 04-23-2002, 02:51 PM
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for what its worth, i use to have the light come on intermittently when i was in heavy traffic, stop and go, etc. then one day it stayed on when i strated the car and i changed the alternator with a VW one, they are the same according to the bosch manuals and its the same output. anyways, its working fine and no lights anymore. ken
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  #12  
Old 04-24-2002, 02:45 PM
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Had the car towed since it would not jump start to my local MB tech who tested the car and said it was the alternator. I took it off the car and drove it 2 hours to Raleigh to USA Muffler & Auto who swapped it out free of charge for a BOSCH ALTERNATOR/REG. Drove back to my local MB tech who is mounting it for me.

Things I learned:

Always get BOSCH PARTS!
Pay attention to the dash lights
Keep some tools in your car
Drive the car home and DIY if possible

Thanks for all the help!
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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

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  #13  
Old 04-24-2002, 04:19 PM
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I had the same problem and I was wondering what it was.
The E-Brake light, brake pads light, and the charging light were all on.
I drove it for two days until it finally died.. and it had to die at night. Good thing that the lights still sort of worked and I could get the battery charged and the next morning got a replacement alternator.

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