300SL new owner BIG problem!

brittone05

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Hi everyone, I am new to the board and hoping to find some help and advice.

My husband has just bought me a 1993 300SL convertible as an early Christmas present. It needs some attention but he got it via a friend so we are happy to put the money into it ( and I am totally over the moon as this is the incentive I need to pass my test! )

The lady owner previous to myself had an issue with a flat battery and when she attempted to jump start it, she connected to donor vehicles engine and battery and proceeded to connect the leads to the SL battery back to front!

This caused major burns to her hand and major blow out to the car.

The battery will now not hold a charge on it's own but will, with the aid of a booster pack, start the engine which appears to run fine?

When the ignition lights come on, the dash lights are all flashing on and off also.

Could this be something greater than replacing the alternator, battery and checking any fuse links?

My hubby is a mech but has been out with ill health for a couple of years so I will probably be out doing work on it with him as he isn't supposed to be in the cold or damp due to his chest problems.

Thanks in advance for any help, advice or suggestions you can pass :)
 

television

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Hello and welcome with you not such good news:(

The first thing to do is to take off the battery and charge it,, then join an ammeter in series, then remove the fuses 1 by one till you find the source of the drain. I would avoid to keep jumping the car
 

ben12345

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Also, with the engine running, use a voltmeter at the battery terminals to determine what voltage you have there.
With a running engine it should be about 13 or 14 volts, to indicate charging.

If its less than that, I would hazard a guess that the alternator went pop with the mistake in jump starting.

Once you have a decent voltage, then it's probably worth replacing that battery too... If the car hasn't been used much and the battery has been allowed to go very flat for any length of time, chances are that it won't take a good charge any more.
 

mayfair

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can anyone help me. i have a year 2000 mercedes e200 kompressor. having problems starting. insert the key turn it on will not start. someone said that the sam control unit is at fualt. can anyone help .thanks mayfair.
 

Rappey69

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hi mayfair. Would you mind starting your own thread on your problem as
putting it here would mean many with possible help will not see it.
 
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brittone05

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Thanks Malcolm and Ben :) We have a few plans for the car once the problems are sorted - I shall get my hubby's electrical testing gear out of the toolbox tomorrow and we can check all the fuses and such and will pick up a new battery for it.

Will keep you all informed as to how it is going and get some pics up once she is polished :)
 

grober

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At that model/age of car you may well have an OVP relay which is designed to protect the engine ECU and ABS system among other things. It is normally situated behind the battery and has 1/2 fuses on top of it. I bet these are blown also. I would second the suggestion to renew the battery if you want a totally reliable source of power to trouble shoot the electrics. If the diodes on the alternator rectifier pack are shorted ---extremely likely---- they will rapidly flatten any battery ( e.g. overnight) since they are in direct contact with the battery and would have received the full blast of any reversed jump lead polarity
 

television

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At that model/age of car you may well have an OVP relay which is designed to protect the engine ECU and ABS system among other things. It is normally situated behind the battery and has 1/2 fuses on top of it. I bet these are blown also. I would second the suggestion to renew the battery if you want a totally reliable source of power to trouble shoot the electrics. If the diodes on the alternator rectifier pack are shorted ---extremely likely---- they will rapidly flatten any battery ( e.g. overnight) since they are in direct contact with the battery and would have received the full blast of any reversed jump lead polarity



Yes he does have a OVP relay

this is the starting circuit as you said the Alternator is permanently wired to the battery

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1992/300E/SYSTEM WIRING DIAGRAMS/4178.pdf

I wonder if that saved the day
 


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