I have a '69 Roadster with an unusual problem. Last fall I went out to start it and found the battery dead. I had just driven it a day or so before, so checked for interior lights left on (the usual culprit), but that wasn't it. After a slow charge, I started it, drove it a bit, and everything seemed OK. The next day, same thing. I have a battery quick-D/C, so I used it. When I next drove it, the problem became clear. When I turned off the ignition, the radio / CD changer continued to play! Subsequent investigation showed that all accessories were live -- wipers, heater blower, and radio, but the key continued to control ignition.

The car probably has 250K+ actual miles. It had 90k+ in 1979 when the odometer decided to quit (speedo stills works, so no incentive to fix it). It was a daily driver for a whole lot of years, but now just a fair weather toy. Because of the mileage, I suspected the switch, so replaced the mechanical switch and door locks. A short drive convinced me that had cured the problem, but I was in the garage a couple of hours later and heard the radio / CD, so D/C'd the battery again and ordered a new electrical ignition switch. I replaced that with the same result. If I just drive it a short distance, the key appears to shut everything down, but doesn't really. Anything longer (five + miles), and it's immediately evident that the accessory power is still on when I turn off the ignition.

As a long-term driver (I'm second owner, and have had it since 1974), I've added things over time. It has a Sony ten-CD changer, an aftermarket radio (which uses the stock wiring), and a cruise control. Those things plug into available switched terminals on the fuse block.

I'm mystified. Someone suggested unplugging the alternator field terminal to test, which I did, but that wasn't it. Anyone have any idea where else I should begin to look?

 

Without an electrical diagram I am just guessing, but it sounds like there is a relay that is staying closed after you turn off the ign. switch.
The suspect relay is providing a path to ground for your accessories.
My .02

 

Of all things, it appears to have been a loose connection at the main 12V from the alternator. I found it by accident when I was doing some cleaning -- when I pushed the wire out of the way to clean under it, it came out of the terminal! I cut the wire back 1/2" to get fresh copper and crimped on a new lug, and no problems since. 'Lectricity sure is strange stuff! Who knew?