So I reached the point where the battery would only hold a charge about a half a week. Since my battery was 3 years old I just figured it was it was time for a new one. No real rush so shopped and around priced batteries. Before I ran out, I decided to check the battery current with all turned off. It has always been about 30 ma but this time it was about 150 ma. This was enough to draw down a tired battery in half a week. With good battery I would not be able to see the problem and it probably had been there for a good while and not showing up till my battery got weaker.

Only took a few minutes to find out the problem was in the radio circuit. Inserted my ammeter in place of the fuse (#40) and measured 138 ma. (The PKE is on this circuit a draws about 8 ma, (130 + 8)). When I disconnected the radio head the problem went away no excessive current drain (measured 8 ma for PKE) (CDM probably OK).

So called Factory Car Stereo and said problem is in the radio head. I took it apart but could not see any visible problems, leaky capacitors and checked a few parts on the power board but all looked OK. So put all back together and will run it into FCS for a look see.

They pulled it apart right away for me as they have just started to see these problems (due to age). He showed me some corrosion in one of the connectors for the CD player. I had this apart but never looked inside of the connector.

He said it was from a leaky capacitor nearby but did not really very much on the surface of the board. I had caught it early enough where the connector was OK and did not have to be replaced and no damage was done to the board. If you don’t catch it soon enough the board can become etched and connector may need to be replaced.

So he called me up and said it was ready and the current draw was just 1 or 2ma. Installed it back in car (temporary) and did all the same tests I had done before. Ammeter in place of the fuse measured 10 ma (8 + 2), and ammeter in series with the battery measured 30 ma.

So I'm back I business and all is well. If you read this far it might be wise (or curious) to just measure the current thru fuse 40 and see if anything is out of line with too much current. I figure you should be in the area of 10 to 15 ma (Radio OFF, Key OFF). (Your measurements might be slightly different from mine due to meters and different modules).

 

It's always good to have a Vendor close by that understands.

Good that you've passed the information on. Parasitic diagnostics certainly can be troublesome for some!!

 

Additional CDM preventive maintenance.
I found this out when I was at FCS and talking to them. I just did not post cause I did not have pictures yet.

There are 4 large capacitors each 470 mfd @ 16 volts. In time they will leak and etch and destroy the small lands around them that go to the ICs. If the board is damaged beyond repair you need a new unit. So they replace these caps for preventive maintenance before they leak. I don’t know what problems the caps might create if the capacitance should drop radically, however I think they might leak before that and cause major damage or problems.

You can see all 4 caps in the first picture, and a close up of each set of caps in the following 2 pictures.

I plan to do this job as soon as I get 4 of the capacitors. I'd rather do this than buy a new unit down the road. CDM comes right out and accessibility is good to get to replace the caps.

 

I just thought I would kill some time and stumbled on this post....I had a similar problem 2 moths ago (July 2020) that my battery may last 2 days and be dead.....What I found was the Bose relay under the center of dash was stuck "on" which supplies power to the speaker amps (in my 88)....There is a wire that supplies power from the radio to turn relay on when radio comes on but, the relay stuck and there was power to it 24/7.

Remove the speaker cover from a rear speaker and pull the connector apart...Obtain a volt meter and after you locate the power wire, measure the voltage to ground...If there is voltage, the relay is your problem.

It is a bitch to get to it but, if (as in my car) you take off the PASSENGER side trim to the center console and snake your hand into the area, you will feel the relay mounted vertically...It is supposed to slide out of it's mounting but, good luck with that...I kept pulling on the relay and it broke loose but, did come off it's mounting...I had hoped to see it by removing my Bose radio but, that was no good...Local generic parts store had a relay for under $15.00, installed it, and that solved the problem...I have a pict of the relay.....After you replace relay into relay "socket" simply stuff it back under the dash and you are finished..

I was looking to see if the problem was solved here but, didn't see it....I did remove all speaker amps and rebuilt all and found that I had one defective speaker which was replaced and 1 defective amp that an IC appears to be bad but, had a spare.....There are 2 large capacitors on the boards and I had difficulty locating exact replacements so, I increase the rated voltage and that worked well...The amps take 2 seconds to come on and that is because the caps are charging up but, at least I don't have that loud "POP" when the radio comes on which is a sign of pending cap failure.

I am NOT sure if this will pertain to other year vettes but, someone searching for a solution for their problem may stumble onto here and gain some wisdom.

I hope this info helps others since I spent 2 days chasing the problem.