I have a 1988 Bonneville SE with the 3800 V6 engine code C almost 185,000 miles. The battery drains far enough down after 2 days of sitting idle so that it won't turn over and start. If I charge it overnight(like I'm doing this week), it starts fine but it dies if I don't keep my foot on the accelerator a little at stoplights. It does seem to idle OK when I first start it up though. Seems to die after it gets warmed up. Idle air control sensor? Throttle position sensor? I took a reading across the battery with my multimeter and I get a little over 14 volts DC but when I checked for AC Voltage it read 30.9 volts AC. Could a couple of the diodes in the alternator be bad? I had the battery(only a few months old) and the alternator checked and they said they were fine. But, they only check to see if the alternator was charging, thats it. Any suggestions would be greatly appreciated. Gary Vancouver,Wa.

GaryH, check the wiring harness in the trunk on the pass side at the top by the hinge area. My 90 was doing the same thing come to find out there was a wire grounding to the chassie.

My 88 had a draw on the battery. It took a long time for me to find it. At first I thought it was the automatic level control as the pump ran a lot. I pulled the fuse so the compressor wouldnt't run but my battery would still drain down after a few days. Long story short, it turned out to be the alternater. I heard a very faint buzzing noise coming fro the alternater, vehicle not running, I disconnected the harness at the alternater and the buzzing stopped. I replaced the alternator and the problem went away. I was told the diode trio in the alternater was bad. Another way to help find the draw is to disconnect the positive cable and connect a test light to the disconnected cable and the other end of the test light to your battery. Your test light should not illuminate at all with everything shut off and the key out of the ignition. If it lights up, start pulling fuses to find the circuit. I found my dome light switches corroded and causing a draw on the battery this way. Just a thought. My 88 has 179k on it and some wierd stuff got corroded.

Thanks for the reply. I've already replaced the alternator since I had a lifetime warranty on it. The battery will be fine during the day(I park it for 10 hrs. a day since I carpool with someone) and it always starts when I get back in it at 6pm at night. On the weekend when I have it in the garage, it will be fine for the first day most of the time but Saturday night it is almost dead sometimes but not always. I'm thinking about replacing the battery cables just to have new ones on the car. I thought I might check the connections at the starter too. I was told that the harness that is in the trunk is worth looking at for trouble too. I've pulled the fuses and really didn't find anything out of sorts. The car runs fine otherwise. If anyone has any ideas what to check, let me know. Thanks, Gary

Here'* a long shot but this happened to me on my 90 SSE open the trunk carefully pulled the material from the passenger side to expose the power antenna and put your hand on it to fell if it is hot or even a little warm. Mine was shorting out and had to be replaced this created a short which drained the battery. good luck

Better yet just unplug the antenna cable in the trunk for one night and see if that solves it.

Load test the batter. You might have a bad cell and whatever charge you put on it from driving, just doesn't include enough amps to spin the starter after it has sat fr awhile. If the battery is good, start chasing down circuits by pulling fuses and seeing it you get more than 2 days on a charge.