thurman_merman

I've searched the topic and haven't had much luck. '91 coupe, 6 spd, factory bose radio, pwr antenna unplugged at the relay in the rear of car. No changes have been made recently.


Sitting in the garage i read 77mA at rest, if I unplug the 10A radio fuse the reading drops to 12mA. The FSM says the radio should pull under 2mA at rest so i'm thinking this may be why my battery dies after a few days of sitting. There are no lights or noises going on in the car when its pulling 77mA at rest so i'm wondering if anyone has had any experience with this. I can't find a troubleshooting procedure in the FSM for parasitic drain, just how to perform the test.

Thanks for the help.

playsdixie

meter the pos cable....keep pulling fuses until voltage drops...fsm will show you the circuit for each fuse....get a test light..have fun...remember...putting your meter in series with the cable will set the ctsy circuit off...make sure door buttons are depresses somehow...then measure the drop...

65Z01

It sounds like you have isolated the draw to your Bose "system".

If the antenna relay is unpluged you may be able to further unplug the amp in the hatch to isolate the pre-amp & amp and further narrow down the problem component.

flyboyslc1

Sounds like you are close to solving your problem. I also have a 91 coupe and my battery would also drain down in about 3 days, then 2 days, then in just a day. So i tried to find out what was going on. I think the factory setting for battery drain is 30-50 milliamp or something like that. I was pulling 68-70 milliamp. If you are at 77ma you are not that much over what the drain should be anyway. For me, the solution was a new battery. I installed the battery and i can come back to the car a week later and the battery still has plenty of reserve in it to start the car. Would i like to get the draw below 50 milliamp? Yea, i sure would. But in a car 20 plus years old, how many of the electrical components are still working within tolerance?

I think you know all this, but here is a video i did


Like the gentleman above said, you need to make sure your doors are closed and the interior lights off. Check those little makeup mirror lights in the sun visors too. The glove box light too. I do not know if they are on the radio circuit?

Let us know the final solution. and good luck to you.

thurman_merman

Thanks, ill try that. Maybe ill get lucky and it will be one of the speaker amps.

thurman_merman

I checked all of the interior lights by glance but I didnt start pulling bulbs individually, its hard to see if they are dim in the daylight. Ill check the radio circuit in the fsm but I dont think there is anything on the circuit besides the radio componets. I'm about to take my battery off the charger and have it tested by a chain store; I used my dmm to check it while cranking and it didnt drop below 12v but so ill try an actual tester to be sure.

Thanks for the replies guys, I appreciate the help.

playsdixie

I wouldn't start pulling bulbs.....check it at night....mirror lites too..they are all on the courtesy fuse....one pull of the fuse will tell you if its that circuit...spare tire lite is on it too... it take awhile to go through the ctsy circuit...been there/done that.....ctsy circuit stores memory for clock/radio so don't be decieved by that amp draw...


great video....wish I 'd seen it before I started looking....

Hooked on Vettes

You may be chasing a Radio problem that may not exist.

Verify in the Service Manual what circuits the Radio fuse powers.

Look at the schematics for the Delayed Accessories Bus. After you shut the ignition Off the CCM closes the Delayed Accessories Bus Relay. This provides power for the Radio fuse and Power Windows circuit breaker for 15 minutes or until either door is opened. The CCM monitors both Door Ajar switches. If either door is opened the DAB relay is de-energized which cuts power to the Radio and Power Windows.

Turn the ignition key to On. Test both doors. Verify the door ajar indicator on the DIC lights when the door is open and goes out when the door is closed. If that checks out turn the ignition On then Off. Verify the Radio continues to work.

Then open either door. Verify the Radio stops working. If it does the circuit is functioning properly and the Radio is not the problem. If the Radio and Power Windows continue to work the DAB relay is stuck closed or the CCM which grounds the primary coil of the DAB relay is bad.

Goldcylon

Make sure your visor mirror lights are not switched on as well. Just a thought

thurman_merman

It turns out the battery was bad after all. The test showed 335cca and the battery is rated for 700cca. I got a new battery but I suspect this is why the previous owner said he was replacing the battery every few years, the constant charging and discharging is killing them. I'm still derermined to find the cause.

playsdixie- I'll spend a little more time on it tonight and see if any lights are staying on. I pulled the ctsy fuse while I was doing my parasitic draw test and it was within spec of what the book said it should draw during sleep mode. The 10A radio fuse was the only circuit that showed a significant drop in amp draw after everything was in sleep mode.

Hooked on vettes- I have verified that the DAB system is working. I'm still going through the FSM to make sure the radio is the only thing on that circuit, if there is anything else on the circuit ill be sure to check it out.

goldcylon- I've noticed the visor lights on while i'm driving sometimes so I have checked to make sure they are turning off properly when the car is parked and they are. I'll double check though, that's an easy one to miss.

thurman_merman

No luck so far. As far as I can tell the radio fuse feeds only radio components. I pulled the amplifier relay under the instrument panel isolating the radio from the speakers and it didn't change the draw. I tried getting to the radio control module but that thing is buried in the dash, I'll mess with it again when I can.

WVZR-1

The CDM certainly requires quite an effort for removal. The video from these I believe helps some with the chore.

http://www.carstereohelp.com/strcorvetteAd.htm

65Z01

When I first got this '88 (3yrs ago) the radio was faulty and drawing current with key Off. Final solution was to swap with a "spare" Bose and voila, problem solved.

Annoyed

Radio fuse protects the Radio components + Theft Deterrent Module

rogergcam

EXCELLENT presentation-THANKS!!!!!

playsdixie

been awhile since I was chasing down a drain, but seems to me those bose amps got power from another circut and needed to be disconnected separately....at least that's what I did..

WVZR-1

He mentioned removing the Bose amp relay that is powered by the courtesy fuse and if he had the correct relay I would guess he's accomplished the same thing. I believe the OP has a pretty good grip on the situation and understands the FSM. It also seems the OP will post back with what he finds.

So long as the OP uses a parasitic draw test that he understands I'd say he's in good shape. The one "flyboyslc1" provided should be simple enough to use but I'm wondering where "Vicki" is during the test. Maybe on break! I like that he used the battery on remote cables.

thurman_merman

Thanks for the link, that will help a lot.

thurman_merman

Which part was faulty? The head unit or the control module?

thurman_merman

From what the FSM tells me the theft system is controlled by the ccm and has its own fuse labeled "theft".

The amplifier relay isolates the amp and all speakers from the rest of the system. It gets its switched power from the ctsy fuse but its load circuit is powered by the radio fuse after it runs through the radio control unit. I'm sure I'll pulled the correct relay because I turned the key on and cranked the volume and got no sound, when I plugged the relay back in the speakers came to life with white noise.

The radio fuse powers the head unit and control unit only, I'll unplug each of them separatelyto find out which is pulling the draw and report back.

I know there is a guy who repairs the corvette bose systems for the corvettes, does anyone have his contact info? I'll send him an email asking if he has seen this before, that might give me an idea on how to fix it.