Why does my car battery run down after the ignition is turned off ?


Asked by May 23, 2015 at 12:51 PM about the 2001 Pontiac Grand Am SE

Question type: Maintenance & Repair

2001 Pontiac Grand Am SE .  installed new battery. tried changing battery posts  Battery will still drain like something is still on.  How do I find what's draining the battery?

3 Answers

Kelly Mayo

Testing for a current drain on your car is very simple and straight- forward. You'll need a TEST LIGHT or a digital volt-ohm-ammeter and a pair of small jumper wires to connect the test probes without having to hold onto them. Remove the negative battery cable, then connect the meter's negative probe to the battery post, and the positive probe to the battery cable. Start with the meter set to the highest current scale. Once it has been determined a lower scale can be used, switch to it without fear of blowing an internal fuse from exceeding that range. There should be no current flow with the ignition switch off and doors closed. If the radio has a digital display, it will have a memory circuit for the station presets and clock. That can draw around 10 milliamps. Some cars from the '60s and '70s had mechanical clocks but even those draw very little current. If you have one that makes a loud click about once every two minutes, that is the self-winder operating. Other than during that operation, they don't draw any current. Be careful to not open any doors or turn on any lights. If you find current exceeds what is expected, remove fuses, one at a time, to see which circuit is responsible for that draw. Most cars will have the fuse box inside so you'll need to disable the dome light(s) to allow the doors to be opened. Many digital meters have a 2 amp internal fuse that may blow if multiple interior lights turn on. As a general rule, a small bulb such as is used in glove boxes will draw about half an amp. A trunk or under-hood bulb draws closer to 3/4 amp. For higher current, look for such things as a sticking power window switch or power seat switch. It's somewhat common for those circuits to be protected with automatic-resetting circuit breakers. If you see a high current draw that occasionally drops to 0 amps, suspect a problem in that type of circuit. An additional clue is the circuit breaker will be hot. They trip from heat buildup and reset when they cool down. If pulling fuses and circuit breakers doesn't stop the current draw, you'll need to look for things unrelated to the fuse box. Although not real common, unplug the generator / alternator. Those with built-in voltage regulators typically have a circuit connected directly to the battery for monitoring system voltage. The circuit may be protected from a dead short by a fuse link wire in the harness. Those can't be easily removed from the circuit like a regular fuse.By the early 1990s, many more computers were showing up and most of them had their own memory circuits, using small amounts of current..even my zo6 will be dead if i let it sit for 2 weeks..

2 out of 2 people think this is helpful.

Thanks to Kelly for that awesome test procedure. You Rock ! One common culprit in these model years are the power door locks.

Kelly Mayo

also forgot this important part.. charge the battery and them load test it first...

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