[lsarg27]

My wife left her lights on last night and she woke me up to jump the car saying she was late for work. So here I go half asleep and I hook up the cables backwards.
The enging started cranking and the dash was all lit up. when I attached the cables the right way it turned over once and tried to start but stalled. Now the ignition circut seems out and it wont turn over. I found the alternator fuse blown and fixed it but no change. No other fuses are blown.

This must have happened before and Im sure the results are the same in most cases.
Can anyone tell me what to look for?
Thanks.

 

[livefreeordie]

Your lucky your battery did'nt explode.

 

[Bazzle]

Fully charge the battery 1st.
Who knows you "may" of damaged some electronic modules too, hope not .............

 

[lsarg27]

Your lucky your battery did'nt explode.

Thanks for the helpful advice.

 

[Bruce R.]

I had a battery explosion in one of my other cars, it woke up half the neighborhood. He's right, you're lucky you didn't have one, the acid is a mess to clean up.

After you get a charge on the battery, turn on/check everything out and find out what doesn't work. Some electronics have circuits that protect them from reverse voltage.

 

[livefreeordie]

You may want to invest in a surge protector for the battery which will save you from replaceing costly parts in the future. Do a search on anti zap or surge protector.

 

[Loi]

Try tracing your wires to the starter or the starter solenoid/relay. Starter is probably fried.

 

[Roarin'Tom]

I assume there was no "warning arc" when you connected the jumpers the wrong way around, otherwise this would have alerted you to the problem right away? If that is right, the battery must have been drawn completely flat, flat, flat. Most common automotive lead acid batteries don't take kindly to that and may not recover from it (plates buckle and so forth). Add to that the reverse connect.... Have the battery tested and unless its healthy start by replacing it. Maybe just your battery that's fried.

By the way, my SLK has a loud warning "beep-beep-beep..." if you take the key out the ignition while the lights are still on. This not the case with your wife's car?

 

[adelaideslk]

probably just change the baterry.

Did you go from positive to negative and negative to positive or did you just have the black cable from the positive to positive and red cable from negative to negative? If the latter it wont matter. If positive on one car to negative on other your blown alternator fuse should be the only prob.

I had a battery explode in a C class years ago - located in the boot - what a mess.

A few years later I had one explode in an E class - located under the back right passenger seat. OMG what a huge mess!

MB batteries have a tendancy to explode. not fun

 

[papa]

We do it all the time on site, If a car had been untouched for a long time and the batt is total dead and will not take a charge, If you put it on charge the wrong way round for 30 secs then the right way 30% of the time it will hold a charge.

But not on the car lol

 

[lsarg27]

Got her back today

Almost 4 weeks later and at a cost of $2700. She is all fixed. A few modules, fuses alternator and battery plus an oil change. I wonder what it would have cost at the stealership? probably 3 times that. Happy to have the top down again.

 

[430]

Ouch.

Glad to hear the car is up and running again.

 

[SLK RICK]

Wow! That's an expensive situation. On the upside, it's an experience you'll likely not repeat (every time you prepare to do a "jump," this whole mess will replay in your mind).

I know the feeling of having my car back after a messy and costly mistake. Good luck to you.

 

[Kirill]

Did you take the money out of wife's shoes budget ?

 

[Hawaiianbrian]

Got her back today

Almost 4 weeks later and at a cost of $2700. She is all fixed. A few modules, fuses alternator and battery plus an oil change. I wonder what it would have cost at the stealership? probably 3 times that. Happy to have the top down again.

Do you know what "modules" were burnt? Or does anyone know where I can begin to check for bad modules? I have done the same thing on my 98 slk 230 and have now replaced the battery, some various fuses including a red 40amp. Now the car still doesnt start and only cranks over 1 ot of ten tries. Every once in a while it will sputter when I turn the key but most tries I get complete silence minus what I believe is the fuel pump pressurizing the system.

 

[Newtoslk]

Do you know what "modules" were burnt? Or does anyone know where I can begin to check for bad modules? I have done the same thing on my 98 slk 230 and have now replaced the battery, some various fuses including a red 40amp. Now the car still doesnt start and only cranks over 1 ot of ten tries. Every once in a while it will sputter when I turn the key but most tries I get complete silence minus what I believe is the fuel pump pressurizing the system.

Did you get your car going again? I'm looking at buying one that has had the same thing happen to it. Should I run or take a chance.

 

[Mike C 3039]

Check the battery condition. Early R170's were fitted with a fairly stupid device (later discontinued) called a K56 relay. This was suppose to isolate the alternator in the event of a crash, mine blew because I got water on the passenger seat affecting the SRS system. If it blows you will get no warning, nothing on the dash etc, the battery will just slowly discharge putting the car into ever worsening stages of limp mode. When mine blew 8 years ago I had a heavy gauge wire soldered across it.

 

[Mike C 3039]

Here's an old post on the K56

https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwiu1qjQqJbpAhVKzDgGHasuBo8QFjAAegQIBRAB&url=https%3A%2F%2Fwww.benzworld.org%2Fthreads%2Fhelp-slk-230-battery-cut-off-relay-problem.1578570%2F&usg=AOvVaw1wORTh9fLonoGqyfvCjE1k

 

[MRPerformance]

Did you get your car going again? I'm looking at buying one that has had the same thing happen to it. Should I run or take a chance.

How long ago did this happen? If it was months/years ago chances are any damage would have been revealed by now, and hopefully repaired. If it happened more recently it'd be worth checking any repair receipts carefully and perhaps talking with the tech who did the repairs.

Even if the car has not been repaired I wouldn't consider it a total deal killer if it's in otherwise excellent condition and it could be had cheap. But if there are any other red flags, or if the car is not an outstanding example at a good price, it'd probably be better just to look elsewhere. There may be a deal to be had if you can repair it yourself but they're not particularly rare (the SLK32 being the exception), so there's little incentive to take on extra risk or spend a lot paying someone else to do the repairs unless the price is very right.

Personally, I'd have zero problem buying a car that had suffered reverse polarity damage in the past, or one that had current damage needing repair, simply because I know that it could be repaired to factory-new condition with a bit of effort. The overall condition of the car, mileage, collision damage, etc, would be bigger factors for me. But I'd want a great deal and I'd expect to repair it myself and still come out ahead.

 

[Newtoslk]

It just happened recently and hasn't been repaired, the car is in excellent condition with no accidents. 1999 w/ 100k on the odometer I can get the car for $2000. Canadian