electrical gremlin

[reliant2]

2000 Lesabre custom, 40K miles, have had four bulbs in the tail of the car blow in approx. 10 days...was driving the other night, lights in the car started flickering, dimming, then going back up to full brightness..checked the driver's information center, the battery voltage was fluctuating between 12 and 15 volts.

The dimming of the lights lasted for about a minute, then things returned to normal. Then it happend twice more that night and once the following morning. Again, voltage meter moving up and down while the lights were dimming up and down.

I immediately suspected the alternator, took it into the dealer...they couldn't find anything wrong, the tech. stated he suspected the alternator, GM won't let him put a new one in the car for free (gm certified used warranty) until they exhaust all other options. Dealer is claiming that they haven't been able to reproduce this problem, have had the car two days now. Battery is fine. They are also unable to explain the four burned-out bulbs in the rear tail-lamp assembly. (parking lights and brake lights have gone out).

I've read that these cars can have electrical problems. Anyone have any idea what's going on? Thanks!

[RABarrett]

Carefully check all of the grounds in the system. make sure that they are tight. Loosen them up, then retighten. This will clean the connection and assure tightness. You might also consider a battery. This is the time in the life of the vehicle that it will probably need one. If the battery is having problems, the internal resistance will fluctuate, causing the ECM to chase the system voltage by controlling the alternator. This is good advice for anyone driving a vehicle with OBDII monitoring. Fluctuating brightness from the lighting or blowing out bulbs is indicative of fluctuating voltages. Batteries are the first suspect in this eventuality. Ray

[reliant2]

hey thanks! dealer is putting in a new alternator tomorrow, no charge as vehicle is gm certified, said they had another 00 Lesabre on the lot, tested it, was pulling a constant 15v, mine was fluctuating between 12.7 and 15...I hope this does the trick.

Pardon my ignorance, which grounds should I be checking? Battery, all light sockets? anything around the fusebox? I know a lot of useless things about cars, but don't know much about working on them.

Thanks

[devon38]

what fixed your problem? was it the alternator?

[reliant2]

yes, seems to have done the trick..haven't blown any bulbs yet and the lights haven't flickered. was very fortunate that it was covered under the warranty.

[RABarrett]

To answer reliant2's question, since the problem affects the charging voltage, check anything affecting THAT problem. If the charging system is affected, check the alternator, its grounds, the engine grounds, body grounds etc. Body grounds are mentioned here since the ECM controls the alternator's output. If a loose ground is affecting the ECM, it may affect other related systems. Ray