I’ve read most, if not all, of the posts on battery drain. My drain across the 15amp fuse holder, second from the top left in the fuse panel, is almost 5amps. My radio would turn on but either no sound or static. Based on great information from the forum, I replaced the amplifier relay. Radio now works perfectly. After closing everything up, waiting awhile for everything to shut off, and checking amperage across the disconnected negative side of the battery, I still have almost 5 amps draw. Not exactly sure where to check next. Any ideas would be greatly appreciate.

 

1) Do you have the Bose sound system?
2) Is the 5 amp drain on the 15a CTSY/CLK fuse?
3) What year is your Corvette?

 

Yes, it’s the Bose. Yes the CRTSY/CLK 15 amp fuse. It’s a 1986 convertible.

 

Thanks for the info: I have the electrical diagram for 1987. That circuit feeds the courtesy lights, alarm module, Bose amp relay and antenna relay. Over 18 lights and other devices. If the light bulb is not lit then you can eliminate it. That leaves audio alarm module, cigar lighter, Bose amp relay, antenna relay, radio, heater and ac controls, courtesy light delay timer and telltale assembly (security indicator).
I would suggest getting the Service Manual for your model year, it has included the electrical manual with all the wiring diagrams and diagnosis steps. You'll be able to unplug the devices one at a time to find which one is causing the drain.

 

Excellent advice, thanks for your help.

 

It sounds like you have a good handle on the electrical stuff, but I need some clarification here. Did you disconnect the battery after everything shut off, or did you have your DVM connected between the battery post and the battery cable at the time you disconnected the cable?

 

I disconnected the negative side of the battery before I replaced the amplifier relay. Then reassembled everything in the dash and reconnected the negative side of the battery. Then I tried the radio and it worked perfectly. Also, turning on the radio allowed the antenna to operate properly. I turned the radio off and waited for the antenna to go all the way down. With the ignition off, the hood open, and the two under hood lights off, I waited for everything else (delay timers etc.) to completely shut off. Then I disconnected the negative side of the battery again and connected one lead of the DVM to the black negative cable and the other lead to the negative side of the battery. Got 4.89 amps with the 15 amp fuse in place. Was hoping for less than .5 amps.
Thanks to MotorCity 87, I know many of the items that run off the CTSY/CLK fuse but probably not all. I have the GM 1986 shop manual with the electrical schematics, but I’m finding it pretty difficult to trace down each wire from the fuse. Some of them end in a numbered block. I’m guessing the numbers in the blocks represent components listed somewhere in the manual? I’m thinking my next step is to just start unplugging components one at a time and watch for a drop on the DVM. I wish there was a listing somewhere that showed each fuse and all the components connected to it.

 

Just a thought. In disconnecting the battery and then "reconnecting" it through your DVM is it possible that you reset the shutdown and needed to wait for the system to shut down again?

 

That’s a good thought. I’ll try it again and give it plenty of time to shut everything down. Hoping for less than .5 amps.

 

Just in from the garage. I disconnected the negative cable on the battery and connected the DVM in series with the negative post of the battery. Got 4.89 amps, but noticed the courtesy lights came on. Kept everything connected, waited, and sure enough, as soon as the delay on the courtesy light turned them off the DVM amps dropped to .02

Thank you RalfKramden and others who tried to help me here. Made my day for sure!

 

Great, glad I was right! However Hot Rod Roy asked the question if you had connected the DVM before disconnecting the negative terminal. That made me think of the system resetting itself once you connected the meter into the circuit.

 

What’s a DVM? Digital Volt Meter? Thanks in advance.

 

Yep, you got it! That's a bit of a mis-nomer though. They'll also measure Amps and Ohms (resistance), so it should be called a Digital Multi-Meter, but DVM is the popular title.