The radio in my '86 740 works fine, but won't keep it's presets. The original was replaced with a "new" one from a salvage yard, which had matching-color wires. Everything works OK, but presets don't stick. Here's the wrinkle: This car has some defect in the wiring that causes the battery to slowly drain, so the previous owner installed a beefy cut-off switch which gets turned off every night. The old radio kept it's presets, even shutting the switch off. If I could get a look at the radio wiring, I could isolate the memory wire and bypass the switch. but I can't find the info anywhere. Anyone out there who can help?