I have a 93 S-10 Blazer LT and the clock on the factory radio doesn't shut off when the ignition is turned off. It takes a couple of weeks but completely drains my battery. Anybody know how the clock is wired? It's not wired to the radio fuse or instrument cluster fuse. I really could care less if I even have a clock. If I knew what wire it was I would just cut it

 

This could be in the key switch and not the radio. The clock comes on when the key is in "Accessory" or "Run". Wiggle the key and see if you can't get the clock to go off. Can you turn the radio "on" when in this state? If so, it's your key. I can't imagen the clock circuit in the radio has gone bad.

 

Thanks. I will try that. I was hoping to not have to swap out the ignition switch but I guess whatever it takes. It would prob be easier than taking the radio out just to cut the wire going to the clock

 

there is no wire for the clock. the radio is simply doing what it's supposed too, comes on when it receives power. it would take a year too drain a battery from that little ole clock...simple solution for now would be to pull the ign fuse or disconnect the battery until you find the problem....

 

I think he means the DISPLAY is always on.. and that would drain a battery in a couple weeks
If the actual radio turns off with the key off then I doubt the problem is in the ign switch

There are three power inputs to a typical radio:
Always on - to hold presets and power clock logic. If you find the fuse for this and pull it i'm betting the display will go off.
Accessory - provides radio operating power and drives basic display illumination
Instrument lighting - which controls radio panel illum and affects display brightness indirectly

Obviously the clock is always running when the battery is connected, it uses the same input as preset memory and doesnt use any power to speak of. But the display should not be lit.

Added Note: See below, the problem is indeed associated with a chip.
Makes sense that all functional switching be done in a big chip and that includes radio function logic. It doesnt take any more power than a watch or phone memory so why not just run that chip all the time. I suspect re is a shorted output gate the chip that should tell the display power to turn on or off.

What has probably happened here is that a diode or transistor inside the radio has failed and the clock display is pulling power from the memory power supply.
Mind that the failure could actually be inside a chip. Practical fix then is to replace the radio. Cutting the wire that supplies it would require resetting stations every time you turn off the car.

 

Update: I pulled the radio bezel off and slid the radio out far enough to cut the orange wire from the radio to the battery. The good news is the clock/display is off and is not draining my battery anymore. The bad news is I no longer have a radio. It powers on but its just static and you can't switch from AM/FM or manual tune. I'm just going to buy a new "radio" at some point and the bezel to fit a standard sized deck. Crisis averted. Thanks for the help guys.

 

great..!! glad it wasn't the ignition....my schematics show that orange wire with a 10 amp in line fuse so guess it does more than hold memory & clock...lol ah well, start singing....