Hello Everyone,

I am having electical problems with my 04 Buick LeSabre, Custom. I got the car about 8 years ago with only 36000 miles on it, now has about 163000. It has the 3800 series II engine, 5 button Driver Information Center and tachometer. It is bone stock.

Earlier this summer, the bell would ring and I would get a random "Trunk Ajar" message in the DIC. The message only lasted a second or two, and on examination, the trunk lid was perfectly secure. Then, on occasion, the automatic door locks would not work. Usually, shifting to PARK unlocks the doors. In this state, the door locks would not respond to the switches or the remote, I had to manually unlock the door to get out. Then, for some unknown reason, the issue would resolve itself and the locks would work as expected.


Then one day I started on a trip, and the entire dash seemed to go out - fuel and temperature gauges dropped to zero, "PRND321" light went out, radio stopped working. Speedometer and tach continued to work. I returned home, disconnected and reconnected the negative battery terminal, restarted, and everything was fine, but I noticed the "BATTERY STATE" in the gauge info was much higher than normal - usually it'* 14.1 plus or minus a few tenths, but now it was 14.8 to 15.1. While the car was running, I confirmed the battery state by measuring at the battery terminal, at the alternator, and at the fuse boxes, all readings confirmed the number reported in the DIC. Figuring the alternator was failing, I swapped it out for a reman, ran it for 4 days, with no change, the battery state continued to be about 1 volt higher than normal, so I swapped back to the original alternator and returned the reman for a refund. At this point, I took it to a repair shop, they drove it around a bit and could not replicate the trunk ajar or door lock problem and for $60 informed me that the battery state of nearly 15 volts was normal, and I should come back if the problem got worse.


So then I started poking around and discovered two grounding connectors in the trunk, one on each side just in front of the taillights. The one on the driver'* side had come loose. I clicked it back into place and have not had any more TRUNK AJAR alarms or door lock issues, but two issues remain:


1. The battery state continues to run about .75 volts higher than normal. When I start in the morning, it is 15.1 volts, as the car warms up, it drops to about 14.7-14.8, and when the temp maxes out at about 220F, the battery state goes as low as 14.5-14.6.

2. The interior lights sometimes don't work.


Usually, when I shut the car off, removing the key causes the interior lights to come on, but now that fails fairly regularly. Also, when the car is off, opening a door will normally cause the interior lights to come on, this is also failing regularly but not always.


So I found a relay in back seat fuse box, #51, INT LP, that seems to control the interior lights, made up some test leads that I could push into the relay socket and did some testing with my multimeter. Normally, when I get out of the car, the lights come on, I close the door, and about 30 seconds later, the lights dim and then go out completely. Or if I leave a door open, the lights stay on for about 10 minutes, then dim and go out. I've bench tested the relay, it is good, I've even swapped it with others with the same result.

Before we go further, let'* clarify the four relay terminals. Two of them, 85 and 86 are the signal terminals that open and close the relay. The other two, 87 and 30 carry the load. When the lights are on, 30 and 85 have positive voltage, about 12.5 when the car is off, and 14.5-15.1 when the car is running, The other two have continuity to ground.


What I discovered is that when the lights should be on but aren't, the voltage between 30 and 87 is only about 0.8 volts. I also discovered that the dimming function before the lights go out completely is accomplished by raising the voltage on the 87 terminal and disconnecting it from ground. When in this state, with the car not running, the voltage on the 30 terminal is about 12.8 and the voltage on the 87 is about 12.0. If the lights are going to work, opening a door drops the voltage on 87 to zero, and continuity to ground is reestablished, and the lights come on. If the lights don't come on, it'* because voltage on the 87 terminal remains at about 12.0 and there is no continuity to ground. Also, the relay terminals stay on until they time out at about 10 minutes.


Last night, I closed the doors with my multimeter on the 87 terminal and ground and the voltage stayed at 11.9 all night. This does not seem right to me - after dimming the lights, I would think that 87 should go to zero volts and continuity to ground and the relay should open to keep the lights off, but that'* not happening. Can anyone tell me what to do to resolve this issue? I would like to get the BATTERY STATE back down to about 14.0 normally, and get the interior lights to work reliably.


Thanks,

Mike

These have a lot of issues with corroded connectors and loose or corroded connectors and grounds.

I would suggest going through the electrical system, especially behind the fuse blocks, and verify all connections are clean and secure. Wires, crimps, plugs, fuses, relays, etc.

Thank you for the reply, that'* going to take a while,so in the meantime, can anyone explain how the alternator output is regulated? I'm guessing it is computer controlled, but I have no idea which computer is responsible.

The very first thing to do is to clean the engine and body grounds. Take them apart and sand to clean metal.

Thanks 007. So far, I have found 8 major grounding points, cleaned and tested them all. There are two in the trunk, behind the carpet, in front of the taillghts, two under the back seat on either side, two in the lower front corners of front door jambs, behind the plastic trim, and two in the engine compartment, one underneath near the starter and one on top, directly below the brake fluid reservoir. If there are more, please let me know.