Interesting electrical issues ...maybe a fix.
 

Thought I would post my experience here of my recent issues. The past month or so my 1989 was showing signs of odd electrical issues. The alarm would have a lot of trouble DIS-engaging. I would try to start. No start. Try to start again and the alarm would go off. The digital readout screen would go all lights...then "TYPE-06 Display" would appear for a second then nothing. Disengage alarm again , try to start, alarm would go off and the cycle would start again. This would go on sometime 2 or 3 tries and then lately it would just continue for several tries sometimes resulting in the car not starting at all. Also i was getting ODD relays clicking while driving when they shouldn't, buzz noises that were new to me.

I checked my 1 year old battery. It was reading just barely 12 volts. Even after charging it was just read 12v or just under. Took it back to Autozone..tested bad. Exchanged for new one, Installed and so far all is well.

Point of story is if your battery is border line failing ( putting out minimal charge ) these and other issues will show their hand.

Not saying this is a fix for YOUR electrical problems but it may be something to look at. I had no idea a borded line battery would cause this kind of problem.

Cool. :)

Update...

The battery I had was a Auto Zone battery. It was replaced under warranty when this issue happened in April of 2011. I JUST replaced THAT battery in November of 2011 for the same issue. Both batteries tested bad and would not hold a 12 volt charge. 2 new batteries in one year???

Has anyone had problems with Auto Zone batteries??? When I exchanged this last time I went to the GOLD series...hopefully that will help.

Doubled checked the in car charging and the alternator is putting out 13.8 volts so thats good. I can't think of a reason these could be going bad. Just bad fortune or could there be another problem I am not seeing. Its a regular driver ( at least 2 or 3 starts a week ) so long periods of not running is rare.

Sure is possible to get a bad battery
I had 2 in the same year they were Bosch from pepBoys

My Autozone Battery on the Euro is still going strong. I bought it when I first started my Euro Project (Dec 2007). I actually like them better than the Wal Mart one I already had to exchange in less than a year.

I purchased an Autozone Duralast Gold in June 2010 and have had no problem. However, I think I usually have less than 3 starts per week.

RE: Auto zone batt
 

Hey Guys, i put an allstate battery in my car in since 2006 and its still running strong,
its a bit expenses ,but it will last long time. Ed.

Autozone batteries are made by Johnson Controls same as walmart ones. They are the number one batteries in Europe and South America. They make the Optima battery here too. Should be a good battery.

It's a pity Optima don't make a battery short enough to fit, I've been running a red top in daily drivers (same battery, 5 cars:D)since 2000.

I heard the Optima 7586DT does fit, but it a little tall so you need to make sure to keep the plastic cover on the + Cable. I can't confirm this since I don't own an Optima.

Dean, I would confirm the drain on the battery with all the doors etc shut. Sounds like you have excessive drain.

Also, servicing your grounds would not be a bad idea.

FWIW I have had Autozone batteries in 2 daily drivers (one battery is still going after 4+ years).

And the warranty replacement is pretty good.

I have the grounds clean. The reason I noticed the dead battery was the blinking alarm light stopped blinking. I know there is always at least THAT as a draw. How can I measure the draw? What would be considered excessive?

Problems

[Quoted]-read second paragraph

Battery Current Drain

The typical vehicle battery current drain should be less than 100 milliamps (.10 amps) and typically
is less than 50 milliamps. This current drain will result in about a two week period without the engine
being started frequently or having an external charger to maintain an adequate charge level for starting.
Some early Porsche climate control units, e.g. Porsche 964/993, had a problem of not fully turning off
once the ignition key was removed, causing the battery to have inadequate capacity to start the engine.

To determine which ECU or what area of the vehicle is causing the excessive drain, the drain must be
monitored by using a clamp-on amp-meter or connecting an amp-meter in series with either battery
lead. Then each fuse of the vehicle is removed and replaced one at a time as the current drain in
monitored. Once the drain problem is localized to one particular fuse, each ECU on that fuse must be
further analyzed as the possible source of the excessive drain.

Some ECUs on a CAN bus system may not fully power down, i.e. enter the 'sleep' mode, and cause
a battery drain problem. The ECU that is causing the drain may not be the actual primary cause,
but failed to power down because another ECU on the bus may be communicating with that ECU,
resulting in the other ECU being the problematic ECU in the excessive battery drain.

No 928 models have CAN bus. There are also many unfused circuits - so its at least possible you may not find it by removing fuses - still worth starting there. Clamp meters usually don't work well for low level DC current - simpler to use a direct ammeter - make sure the interior lights stay off.

Alan

Typically a 12 volt battery should read about 12.56 volts fully charged, no load and around 13.8 volts when motor is running. If the battery starts reading 12v soon after charging, then it has a problem. At least that is what I have run into myself. Naturally, there are things running when the car is off, such as clock, maybe alarm etc. Kind of crazy, my girl friend just replaced the battery in her Buick, it was 8 years old! I never have that luck! I was told heat is the main destroyer of a battery, but ours are not near the motor so you would think that would help extend the life.

Heat and vibration kill batteries, but so do periods of less than full charge. Most of the batteries in my 928's have been drained dead flat 0v half a dozen times or more for a month or more at a time. I've gotten as little as six months and as long as almost 5 years.