I made a really stupid mistake tonight. A guy asked me for a boost. In the process of connecting the positive and negative terminals I got them reversed. Yes it did spark but didn't think anything of it (second stupid mistake). About a few seconds later (maybe 3 to 5), I notice smoke from the cables which I immediately disconnected. While the cables were smoking, the car still ran but noticed my ABS light on. As soon as the cables were disconnected, the light when off. I reattached the cables properly and the guy's car started. I drove my home (1991 240) with no problems. There are no apparent electical problems that I have noticed. Everything seems to right alright.

However I am wondering whether I did cause some electrical damage that may become apparent at a later date as a result of mixing up the cables. Is there anything that I need to look at specifically or is everything ok and I'm just being paranoid. Has anyone else made this kind of mistake besides me?

Thank you for your kind reassurance.

Since all seems to be working, I agree with everyone else that you are ok.

From your car's perspective, the discharged battery would have been seen like a very big electrical load. Your alternator would have probably seen a voltage drop, and the regulator would have increased the field current to run it up to full output. If it's still working, then sounds like not fried. Everything else would have just seen the voltage drop, but not invert.

I think the greater chance for damage is the other car. Depending upon it's battery's state, it may have seen the voltage invert, which would have the greater potential for damage. On the Volvo, I could see that harming all of the various computers, and likely so any other reasonably modern car. OTOH, the resistance of the cables, and the clamps, and the connections at both ends, with the very high current load, may have been enough resistance to make it so the other car didn't go too negative for too long. If they drove off, then maybe they are ok, too.

Roger

'95 854T 259k miles
'93 945T 218k miles
'87 245 M47 299,500 miles and counting

Thanks Roger for your reply. It's been a few days now since the incident and the car is running like nothing ever happened. I am sure glad that I got lucky this time! I always remove the negative battery terminal when doing certain types of maintenace work therefore it's beyond me why I put the positive cable to my negative terminal!! Thinking more about it, I think that I was distracted when seeing the red rubber covering on the negative battery ternminal cable which made me believe that it was in fact the positive (however if I had looked closer I would have seen the negative symbol).

What I will do is cover the red rubber with black electrical tape in the event that I ever have a moment of mental weakness again! Lesson learned.

Like everyone else. You dodged a bullet.
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Post Back. That's whats makes this forum work.

Thanks again everyone for giving me some peace of mind!

A long time ago I did the same thing on my VW bus. A mechanic told me that because my engine was running the entire time, no problem. The fuel injection computer(?) was still OK and there were no problems.

Sounds like you got lucky.
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My name is Klaus and I am a V♂lv♂holic

Thanks for your reassurance. Despite the car's age, and mileage, 310,000km, it still looks and runs very well and it would have been a shame for the car to have die that way (dependig on the extent of damage of course). However it would have died helping another motorist - which is by no means any consolation!! As for the other car, it started fine and the guy drove off but I'm wondering if it sustained any electrical damage?

As for my car is it possible that the alternator may have lost its effectiveness and now has a shorter life spam because of my stupidity?

Thanks again for your reply.

As with me, the cables took the brunt of the damage. Your alternator is fine, the voltage regulator prevented it from cooking. The only damage would have been to smaller wires that got overloaded, but your fuses are fine so that is good news.

My positive clamp melted!! I had to buy new jumper cables. The car ran for another 10 years.

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My name is Klaus and I am a V♂lv♂holic

The fact you drove it home without issue is a good sign. Beyond that, time will tell.
Dan