CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Dead battery

i have a 2000 silverado 2500. all of a sudden my battery went dead. battery was 6 months old.replaced it. i buy the best battery i can fit in it.after about 1 month that battery went dead.i noticed a spark at the positive cable when i hook it up. is this a short?

No,it is called a parasitic draw.What about the underhood light.If you disable the light do you still have the spark?

yes. i recently put a used snowplow on this truck.i put a brand new motor on the pump.could this be drawing too much power that it is killing the battery?

If you know the current draw of the truck, added to the current draw of the pump, and compare that to the output of the alternator, you’ll know if you’re demanding too much of the alternator. If the current demand is more than the alternator (at the rpm and duty cycle of the alternator) can provide to, both, the truck and pump, there may not be enough left to charge the battery.

The pump motor is presumably used only to raise/lower or otherwise position the plow. If you aren’t doing any re-positioning the pump or motor shouldn’t be drawing any power at all.

It’s unlikely the plow itself is your problem, although the plow’s INSTALLATION might be the source of your trouble. Make sure no wires (on the plow or on the truck itself) have been pinched or cut. You can check for an excessive current draw by putting an ammeter in series with the battery, between the battery and the negative battery cable and check the current with nothing running. If you find a reading with more than a quarter of an amp you can track it down by pulling fuses, unplugging things, etc. DO NOT TRY TO START THE ENGINE WITH THE AMMETER INSTALLED. The starter current will immediately destroy the meter.

You say you see a spark when you connect the postive cable,why is a pump motor that is turned off suspect? There is a difference in a parasitic draw and a load that is so high your charging system cannot compensate for,search for your parasitic draw.

i now notice one “electrical?” problem. when i fill the gas tank my gas gauge bounces from empty to full whenever it feels like it until the tank gets about half full. any relation? thanks to everyone who answered!