If the lights did not come on when the jumper cables were removed, your battery is defective or run down. Jumper cables are very ineffective at starting an engine in a car with a dead battery because they have such a little contact area with their cable clamps. You just can't get enough current through them like you can with the car's battery cables. For that reason you have to connect the cables, then let the rescue car idle for a few minutes to charge the dead battery. That will work if the dead battery is still good and was just partially run down.
If the dead battery has a shorted cell, a jump-start may never get the engine started. The generator in the rescue car can't overcome the shorted battery and wimpy jumper cable connections, but more importantly, it can be damaged, particularly if it's in another GM car.
If your battery is good but it just ran down from leaving the lights on, it could be so far run down that it will take up to 15 minutes for the acid in it to become conductive and it STARTS to take a charge. You would see that on a battery charger by the amp meter staying on 0 amps for a while, then slowly rise as the battery starts charging. The same is true when jump-starting it. You'll need to leave the jumper cables connected with the rescue car idling for 10 - 15 minutes before trying to start your engine.
After your battery has been charging a few minutes, remove the jumper cables or turn the battery charger off, then measure its voltage. If it's 12.6 volts, it's fully-charged and there is some other problem if the engine doesn't crank. On GM cars that is usually due to the security system which is pretty effective at locking owners out of their cars. If it cranks slowly and the lights get dim at the same time, suspect a corroded or loose battery cable connection.
If you find around 12.2 volts, the battery is okay but it is discharged. If you find closer to 11 volts, the battery has a shorted cell and must be replaced.
GM also has a huge problem with their generators since they redesigned them for the '87 model year. Once you get the engine started, measure the battery voltage again. It must be between 13.75 and 14.75 volts. If it's low, replace the generator. If it's okay but you still have a dead battery every few days, it likely has a bad diode. When one diode of the six shorts, you will lose exactly two thirds of the generator's output capacity. That leaves you with 30 amps from the common 90 amp generator, and that isn't enough to run the entire electrical system under all conditions. The battery will have to make up the difference until it slowly runs down. You'll need a profession load-test to identify that. "Ripple" voltage will also be very high.
It is common to go through four to six replacement generators in the life of a GM car. To reduce the number of repeat failures, replace the battery at the same time unless it is less than about two years old. These generators develop huge voltage spikes that can destroy its internal voltage regulator and diodes, and can interfere with computer sensor signals. As the battery ages, it loses its ability to dampen and absorb those spikes.
Saturday, October 12th, 2013 AT 1:04 PM