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I recently changed a dead battery for a new one. When I drove the car, no problem. But when I turned it off, the alternator light went on. Car was off but light was on, even if key was out. Light was not on when I was driving or idleing. I've read what the problem is if it is on when running or idleing, but what is the problem when the car is off? I have unhooked the battery now so that the warning light does not drain it. Any help would be greatly appreciated as I am a "newbie" and would hate to bring the car in to a mechanic if I can take care of this myself(Or at least know what I'm talking about if I do bring it in).

Thanks in advance,

Sean
1965 Mustang convertible
 

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I'm not 100% sure but it sounds to me like you may have a bad ignition switch. It's normal for the alt. light to be on when listening to the radio in the accessory position for instance so it sounds like the ignition switch may be faulty and supplying current to some system or other and the alt. light is simply reporting the drain. Hope that helps. :) ;)
 

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I'm thinking the same thing as DB65. The switch isn't completely turning to the off position even though the key is.
 

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you are probably getting 12 Vs on the accessory position of the ign switch when its suppose to be off. try wiggling and tapping ign switch and see if it goes out. does radio play when you turn it on with ign key off in this condition?
 

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I have a 1965 fastback with a 289 4v that I purchased last October. I had many electrical problems that I sorted out with the help of this forum and by reading/studying the electical schematic and two elecrical handbooks. Haynes Automotive Electical Handbook and HPBooks Automotive Electical Handbook. You can find the schematic on this forum and print it out. No short cuts as you must doggedly follow each wire to see if it is still connected properly after all these years and previous owners. You may need to just replace the switch if all is connected properly. When you get it sorted out you will feel a great sense of accomplishment!
 
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