I have heard that jumpstarting a car with a bad alternator can kill my alternator…is this true and why ?

The last time I made that mistake, it cost me about $60 for a new voltage regulator (on a car that had a separate voltage regulator).

I understand that the voltage surge from jump starting can damage the ECM and PCM. The solid state devices are not designed to sustain this surge. Has anyone else heard this? I certainly agree that certain solid state delivers can’t take a surge, but it seems to me that this could be avoided by b…

Jump starting shouldn’t cause any sort of “voltage surge.” Both cars have 12V electrical systems, there’s no where for a voltage surge to come from. The electronics are damaged by the reverse voltage that results from connecting the jumper cables backwards on one of the cars.

My wife has a set of “foolproof” cables in her trunk. Even if the polarity is reversed, the unit senses it and makes a correction. They don’t cost tmuch more than a regular heavy duty set.

That’s a good idea. One time I gave a jump start to a guy who had the red cable on the negative terminal and the black cable on the positive terminal. Fortunately, I realized it before I connected the cables. Now I always make sure to confirm the terminal polarity by looking for the “+” and “_” s…

The donor car does not have to be running for a jump start to work. It is, however, good practice for it to be running. The reason is that while you are trying to start the bad car, you might run down the battery of the donor car and then you would have two dead batteries. If you keep the donor c…

"I have no idea what you are talking about with “kilovolt systems.” " The ignition system converts 12 VDC to 50,000 VAC. That is what I meant, and I believe what the expert mechanic on Motor Week was referring to.

Okay, but I don’t see what that has to do with the subject at hand, jump starting a car. The 30 to 70 KV spark discharges certainly don’t make it back into the 12V electrical system.

I like the idea of a difference of potential between the donor and the donee to promote the flow of current,the higher the difference the more current to flow,hence the running donor. It helps keep the donor voltage from being pulled down to the level of the donee,when that happens no current flows…

Jumpstarting...can it kill alternator?

General Discussion

jtsanders November 5, 2009, 12:16am 44

If that’s the case, why does the donor car have to be running for a jump start to be successful? And both cars have kilovolt systems as well. I believe the idea was that after the cables are connected to both cars, the donor car is started. That’s when it might occur.

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Jumpstarting...can it kill alternator?

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