chevy truck radio battery

I have a 1999 Chevy 2500 6.5 diesel. when i shut the truck off the clock stays on, radio wont turn on though with key off. when i take out the fuse that says "radio batt" it goes off. Everything seems to work normally with key on. It drains the battery over night though. Could anyone help me? I am new to the site.

thanks

Cal

hi, assuming the radio stays on with the key off and doors open or shut, do the power windows operate also? in the dash fuse panel, remove fuse 17 (radio) ...does the radio turn off? mark

hi

the radio doesnt stay on with the key off, just the clock. It has manual windows. The clock is on all the time, unless i take out the "radio batt" fuse.

calvin

i will check and see if radio turns off when i take fuse 17 out

calvin

the radio turns off when i take out fuse#17

calvin

fuse 17 is labelled radio?... the radio maintains previous settings..clock and stations even with said fuse removed? the vehicle may have retained accessory power, which is supposed to turn off if a door is opened, or a fixed period of time. since pulling that fuse turned off the radio, either the relay that supplies power for that circuit is defective, or the module controlling it, is activating it improperly. you've tried disconnecting the batteries for several minutes?

you also could have an issue with the ignition switch.

yes fuse 17 is the radio fuse. yes it keeps the stations set and clock set right when i take it out. Fuse 19 is radio batt. When i take it out when the key is off the clock goes out but i also lose my station settings and the clock goes to 12:00. So i think it would have to be in the radio batt circuit. maybe there is a relay in that circuit that is defective? i havent had the batteries unhooked but, they have been drained due to this problem many many times. I also think it could possibly be the ignition. or maybe it could be the radio itself? Im not sure what step to take next i know that the ignition switch will cost $235.00 and i could probably get a radio from a wrecker for $25.  i apprieciate your help very much.

Calvin 

Remove the radio from the dash, using a volt meter, check the voltage on the yellow wire with the key in the off position.  Unplug the harness from the back of the radio when checking.  If there is voltage on that wire with the key off, there is a problem with the truck wiring.  Plug the radio back in and check voltage again.  If there is now voltage on the yellow wire, there is a problem with the radio itself.

do you have a test light and ability to disassemble the dash? you're looking for the wiring leading to the ignition switch...should be able to remove lower dash panel crossing beneath steering column. the ignition switch wires are rather thick...think fatter than spaghetti. you'll want to test the dark brown for proper operation....make sure it loses power when key is turned off and key removed. if it does your ignition switch is fine. the retained accessory power relay i believe is on the fuse panel on the left side of the dash, but not sure 100%. if you find it, removing it will power down the radio. then you'd need to test to see if the relay is defective or the control module is.