I am a Canadian living in France. I bought a "voiture sans permis" (JDM Simpa) for my son to go to and fro school... It is essentially a very small motor vehicle which can only go up to 80 km per hour. It sat in the garage for about a month. He started driving it September 5, 2018. About the third week of September, we installed a little twelve volt radio, but it never worked. Hooked it up, tried testing out the radio but it didnt work. On October 5, the battery was dead. Since we had very limited options at the time, my son and I put a new battery in the car. I put the old battery on battery charger. My son took the car back to the store to activate the guarantee for the battery and they told him that the alternator was broken and was not charging the battery. My son saw with his own eyes that the alternator was putting out almost no charge. The guy who sold us the car told us that it is our fault because we tried to install the radio. That somehow by trying to install the twelve volt radio (which never worked) we damaged both the battery and the alternator. Is he correct?

  • What's the nominal battery voltage on the vehicle?
    – user
    Oct 22, 2018 at 11:57
  • 1
    I am not a mechanic and I dont know what this means. Currently there is a 12 Volt, 40 AH, 340 A (EN) battery in the car. I sincerely hope that answers your question. The car was not sold with a car manuel, so I dont have much more information than that. Oct 22, 2018 at 13:11

1 Answer 1


I don't think installing or trying to install the radio is going to cause the alternator to fail, (I have installed radios on new cars, old cars, tractors and probably numbered in thousands).

This is most likely coincidence, but, that guy is looking for a way to avoid paying ; very french though...

The comment by @alephzero raises a point: the radio should have been connected to a fused circuit as part of the installation. Some would have connected directly to the battery either with or without fuse, but neither case is likely to have destroyed thew alternator...

  • Well, there's a missing piece of the story, which is "why did the radio never work". I suppose you could have done something that destroyed the alternator (or more likely, the rectifiers and/or voltage control circuit rather than the alternator itself) but I agree with @SolarMike it doesn't seem very likely.
    – alephzero
    Oct 22, 2018 at 8:46
  • I don't know yet why the radio didnt work. To the best of my ability, we did everything right in installing the radio. I wonder if the car motor is too little to support a 12 Volt radio. I have been looking for 6V hidden radios as an alternative, but this is over my budget at the moment, so I merely disconnected the non functioning radio and put the project on the backburner until we can get more money to deal with it. Oct 22, 2018 at 9:45

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