wdurham

I bought a 92 coupe in early July. Among some various minor issues, a battery that keeps draining has been an issue that came along in early August. I was driving it every two or three days until that time, but then I travelled out of state for a couple of weeks.

I returned home to a dead battery. After I charged the battery and went to reconnect it in the car, I noticed the mirror (map) light come on. Ok, my mistake, I must have left the light on. At least that's what I thought. The problem kept coming back if the car would sit for more than 5 to 6 days.

The volts would never read below 14.0, with the engine running, so I felt the alternator was working. Wtill if the car would sit for more than 5 - 6 days it would be obviously low on battery power or just dead.

Today, I finally got a whole day to work on this problem.

According to paperwork with the car, the battery was new in June, of last year (2011). Just to be sure, I took it out and tested it. It tests good, so I put it back in.

I was sure everything was off, all doors closed and hood was low enough not to activate the under-hood lights. Then I disconnected the negative cable from the terminal on the battery. I checked amp drain using a multi-meter (Volts/Ohm/Amp meter). It registered a constant .19A, or 190 mA.

From this forum I see a reference to standard or expected drain being less than 50mA with the car turned off. So something is not right.

Now I was down to isolating where the problem may be. Pulling fuses one at a time and rechecking the draw until the drain dropped was my only real option. After I pulled the 10A radio fuse the amperage drain dropped to 36mA.

Success!! Well, sorta. So, I know my issue is somewhere in the radio system or circuits. It is the Bose factory system, which didn’t sound that great to start with, but appeared to work when I bought the car. I have heard some noticeable “ticking” from a rear speaker, in the last couple of weeks, so that may be the area I need to search.

At any rate, I’m going to start my search on the forum for some details regarding what to test next and where it is located. If you've had some problem related to this, please feel free to drop me some ideas of where specifically to look either in the car or on this forum.

Thanks guys!

65Z01

I had a similar issue with my '88 where the clock stayed illuminated. Pulled the CLK/CTSY fuse and current drain dropped from 260mA to 30mA.
I emailed a Bose repair shop in FL about the problem and he said it would cost $150 to repair the radio.

Dans 85

Wow this sure is a strange one. I would re verify your current draw one more time just to be sure.

The radio fuse should have no voltage whatsoever with the key off and AFAIK it only goes to the radio and not other devices. It should show 0V at the fuse. The 150ma extra draw would seem to me like a relay stuck on as that is about as much current to operate the coils. Thing is though the radio would need to be powered up in order for the amp/ant lead to power the amps and antenna. If there was a fault in the radio it could possible keep the amp relay on, but the antenna would be up too (if it is in working order) and be the telltale clue. That still does not mean either relay could be bad, but if they are 'stuck' on then pulling the radio fuse should have no effect. Very strange problem I must say.


This is what I'd do for now...

Since you have a meter, test the fuse for voltage with the key off. If voltage is present pull the fuse and see if the voltage is on the 'hot' or 'cold' side of the fuse. Hot side will have +12v with key on. There may be something backfeeding this circuit. Stray voltage on the hot or cold side will give indication of where to proceed. Is there anything aftermarket in the car?

Regards,

wdurham

Thanks for the response and the advice guys.

I will double check the amp draw, or rather reduced draw conditions, and the fuse leads.

The car is very original. At least it appears to be. The power antenna does operate as it should, both with the radio powered off and on and with the ignition turned off and on.

I know the family that owned it since it was new. Historically it did go from an adult original owner, to his nephew and then to a relative of both previous owners. The nephew was younger, so I suppose an aftermarket stereo may have been in the car at sometime. There are no visible signs of such a change. I haven't looked inside the dashboard at the wiring yet.

I probably should have pulled other fuses. I stopped after finding this. Pulling the courtesy fuse didn't seem to change anything, which seemed odd to me. I figured. something would have been on the circuit (clock or some minor load).

When I reconnect the ground at the battery, I do hear a relay click or clicks near the front of the car. Also, it sounds like there are relay clicks in the cabin, perhaps on the firewall. Working solo makes tracing these difficult since I need to be at the battery terminal and near the relay to get an idea of what is actually happening.

Cap'n Rich

This likely has nothing to do with your problem, but I thought I would mention it.

Occasionally, when I exit the vehicle, I will accidentally turn on the courtesy light in the door of my '89 roadster. When I close the door, the interior lights stay on for a few seconds. By the time they turn off, I'm halfway to the house and don't notice the left-hand door light is still on.

It goes out automatically after a few days. Then I have to put the battery charger back on. I keep it handy . . .

65Z01

I picked up some red & some black braided wire at Radio Shack, attached roach clips and use these to effectively extend the batt leads to inside the car for convenience of testing.

wdurham

There is no voltage on the equipment side of the radio fuse position. This is the case with the key off or on.

Also, with the key off or on I have 12.03 volts on the hot side of the radio fuse position. Isn't this supposed to be switched?

Dans 85

Don't forget there is Retained Acessory Power and that side will stay hot until you open a door of for 15min whichever comes first. Once the RAP goes away there should be no voltage there.

wdurham

Thanks again for the advice Dans 85.

The hot side of the radio fuse is staying constant with 12 volts. What is the feed for this? I may have a short upstream, or if this is fed by a relay, that may be sticking.

wdurham

By the way, the radio does turn off and on relative to the key being off or on. Even with RAP accounted for the 12v does not go away, even after an hour.

Kmcoldcars

The radio has a switched 12 volt supply to run the radio, and a non switched supply that goes to radio memory and keeps all the preset stations good. Make sure you are not checking that fuse.

wdurham

The clock and presets are powered through the courtesy fuse. My 'stray' or abnormal voltage and amperage draw are on the radio fuse.

To double check basic functions I put the radio fuse back in. I climbed in the car turned on the key and the radio. Radio came on, antenna went up as expected. I turned off the key and the radio stayed on. Again, as expected. Opened the door and the radio turned off and antenna retracted, as it should with retained accessory power.

I rechecked the voltage at the radio fuse. If the radio turned off as described above, I believe there should be no volatage on this fuse position. Wrong, there is still 12v present , so I reinserted the fuse and disconnected the negative terminal at the battery and sure enough I still have 187 mA draw. Pulled the radio fuse and this drops to 34mA.

So is the radio fuse always hot? Does it feed the radio through a relay before or after this fuse to control the RAP feature?

ccrazor

If your 92 is like earlier models the radio fuse should only be hot with the key in accy or run..

wdurham

Thanks, that is what I was assuming. At least I know I need to look downstream (back towards battery) from the fuse to find out where this mysterious 12v is coming from.

I still don't know exactly how the RAP feature does it's function. Before or after the radio fuse is the question.

I know, I know.....get an FSM! Working on that, too.

Kmcoldcars

Photos of the radio circuitry and the DAB circuit. I left them large so you can look at the area you want.

wdurham

Wow! Great support from this site.

I'm on my phone, so the diagrams are difficult to see. I will get on the PC later and see what I'm working with.

Thanks!

wdurham

More fault isolation needs to happen.

Also, a correction to my earlier post. Kmcoldcars told me to be sure I wasn't checking the wrong fuse. Well.....heh heh....

I was checking the Radio Fuse in the Main Fuse Block. I wasn't even aware there was a separate Radio fuse in the auxiliary fuse block. The diagram below clearly states the Aux Fuse block Radio fuse is the switched source.

My issue is definitely related to something draining from the Radio Fuse on the main fuse block. According to the diagram, this fuse is supposed to be hot and is wired directly to the radio head unit.

So I am going to need to get to the back of the head unit and see what may have failed.

Thanks again for the pointers, advice, effort to post diagrams and just general input. It has all been very helpful.

Cliff Harris

I have heard of antennas getting into a weird mode where the motor doesn't shut off when the antenna goes down, thus draining the battery. It might be worthwhile to also look in that area.

wdurham

I may have time to work on this during the rest of this week. Right now it may be the weekend before I get to tear into the instrument panel, and test the next points in the wiring harness and the system. I hope we'll see what the real cause of this issue ultimately may be soon.

Dans 85

2 fuses labeled radio?

Oh well, at least now that we have a diagram we are not chasing pink dragons.

Yes, see if you can unplug that ticky rear speaker (should be a connector right by it) and recheck your draw.