Alright, here's the story:

i just put my new battery in my car... but it was dark out and I accidentally connected the cables wrong and i shorted something out. i think something to do with my distribution or something. cause there was this burning smell and now the car won't start. the starter comes on and tries to start it but it won't turn over. My friend said that a friend of his had done the same thing to his Jetta a couple months ago and that he totally fried his computer. Can anyone back this up or give me any help at all? If it is the computer we're talking huge amounts of money. He also suggested that if it was the computer to go to the junkyard and find my car so I didn't have to pay as much and install the parts myself or get someone to do them for me. Any help anyone can give on this issue would be greatly appreciated. Thanks a ton. In a time of crisis, this message board is my crutch. Gotta love technology.

Shubs
87 300E 124

you may have fried the ECM according to my friend who works ata stereo shop andinstalls batteries all the time.

So it is likely you could have fried something.

On another note. I just put an optima blue top in my car. I took it out of my boat as the boat is in storage,a nd I wanted to keep the battery fresh, plus my battery has been a little weak lately, voltage has been jumping, so I am doing some draining and recharging on it and some testing of the cells to see if tis still going to be ok. Otherwise I'll pickup a new battery when its time to use the boat again.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon

First place to look is the "overload protection relay" and it's fuse usually located right on top of it under a little plastic cover.
It is behind the plastic cover that sits between the fire wall and the battery.

The burning smell- I can only guess, but it is probably not good.

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Alain
independant MBZ tech since 1981
http://www.motorsportlegendsks.com/

Alright, just got the car towed and it's at the mercedes service center. The guy at the service center said that I might have blown a module. He said that he doesn't think the overload fuse can handle something like a reverse in polarity...but I'm keeping my fingers crossed. Hopefully it's just a wire that has gone bad or something since that would account for my burning rubber smell...but then again I could have scorched one of my modules and totally tacked up 1000 bucks worth of damage. If I did blow a module, could I be able to go to a junkyard and just pick up the part for under 100 bucks? Supposedly, the tech said that the 300E's are pretty bad from a wiring standpoint and can't handle much current at all through the wires. We'll see what happens, keep your fingers crossed.
Thanks for the advise so far. I feel really dumb, but I deserve it for doing something like accidentally reversing polarity. I guess I can install my own exhaust system but can't even change my battery. ha ha.

Shubs

Shubs --

If it ends up being the ECM, try to find a used one, first through this site's sponsors, and then Potomac German Auto or others that specialize in MBs. A new one for my 1990 300TE was, I believe, $1800 a year or two ago, but I purchased one from ASAP in Atlanta (now RIP) for around $250. Note that this module very, very rarely fails, and my used one hasn't skipped a beat since purchased, so I wouldn't hesitate to purchase used, particularly given the price differential.

I'm more than a bit gunshy about jumpstarting contemporary MBs with all of the electronics on-board, and would probably simply stick in another battery to avoid having to jump start.

Finally, note that many 80s model MBs can be "tow-started" in times of trouble -- check your owner's manual and it will describe the procedure if it can be done with your car (good to check now, and then keep in mind for emergencies).

Good luck on the outcome.

Richard Easley
Waco, Texas

I have seen this and it is usually the overvoltage relay and the alternator. The reason is that they both use diodes. Diodes prevent backward polarity but can't handle the load of the entire battery.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

I concur that both the OVP and the alternator probably suffered damage.

I did this on my Bug once and fried the alternator. I also fried several stereo components that shared a separate battery, and learned later from a stereo installer friend to install a diode in the negative circuit to prevent destruction in the future...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

I was re-wiring a VW Thing that had burned up, it didn’t have an engine at the time. I hooked the battery up and started checking things out. Lights: ok. Wipers: ok. Starter: without an engine it sounded okay Turn signals: ok. Then I noticed the battery was hooked up backwards

Alright... here's the diagnosis-
Fried Ignition Control Unit... and he said that was only the start since he can't even do any more until he has that in cause their equipment won't read anything until i have that. He quoted me with $1500!!! I already consulted Partsshop and they have it for $1000. Better, but still a lot. I'm gonna go down to the junkyard on saturday morning and hopefully they'll have an early 300E that I can just rip the part from. Anyways, thanks for all your help here. Anyone have any other advise?? like how to deal with junkyard people...how do they know what to charge you for the part?? I heard they just kinda look at what you're wearing and if you look rich and stupid then they'll totally rip you off but if you start talking cars then they just kinda look at the part and guestimate. anyone have any advise?
thanks

-Shubs