What would cause a draw on the battery?

A parasitic battery drain is just something that consistently and continually drains your battery. This could be a faulty relay, a headlight/dome-light switch, alternator, or any other electrical gremlins. Taking your car to a mechanic with an “unknown” culprit can cost you big bucks as well.

How is a parasitic draw diagnosed?

Pull the negative off the battery. Put the test light between the post and the ground wire. If the light illuminates, you have a draw. Use the fuse pull method to find the draw; when the light goes out, you found the draw.

Can a bad battery cause a parasitic draw?

But a battery-power drain can also be the work of a bad alternator diode or even a faulty battery. Depending on the amount of current being drained, a parasitic draw will suck all the juice from your battery in a few hours or minutes.

What is an acceptable parasitic draw?

A normal amount of parasitic draw for newer cars is between 50-milliamp to 85-milliamp current draw. A normal amount of parasitic draw for older cars is a reading less than 50-milliamp. Anything past these amounts indicates an electrical issue and should be addressed by a mechanic.

What can draw on a car battery when the car is off?

The problem generally is not the door or the trunk lid itself, but rather the interior lights that will continue to burn as long as the door or trunk remain open. Even a simple dome light left on by accident will draw enough power from the battery to drain it in a day or two, leaving the battery incapable of starting the car.

What drains a car battery while it is off?

So you ask yourself, what drains a car battery while it is off? Most common reasons why your battery drains is because you left your headlights overnight, clock, radio, and security alarm that runs after your car is turned off, bad charging, defective alternator diode, and old battery.

What should the parasitic draw be on a car battery?

For testing purposes, we will select 2A or 200mA in the amp section of the meter. This is where we can see the parasitic draw on the battery. The reading for a normal vehicle with no parasitic draw can range from 10mA to 50mA, depending on the manufacturer and the amount of computers and features the vehicle has.

How to get rid of negative battery drain?

Remove the negative battery cable from the negative battery terminal. Find the negative cable, which will be marked with a minus sign (-) and may have a black cover over it. Remove the cover, if applicable, and use a wrench to unbolt the negative cable from the terminal.

The problem generally is not the door or the trunk lid itself, but rather the interior lights that will continue to burn as long as the door or trunk remain open. Even a simple dome light left on by accident will draw enough power from the battery to drain it in a day or two, leaving the battery incapable of starting the car.

How much power does a negative battery draw?

Touch a lead to the negative battery cable terminal. Touch the other lead to the negative battery post, completing the circuit within the multimeter, which will display the amp draw. Power draw should be under 50 milliamps. This will display as 0.05 amps.

For testing purposes, we will select 2A or 200mA in the amp section of the meter. This is where we can see the parasitic draw on the battery. The reading for a normal vehicle with no parasitic draw can range from 10mA to 50mA, depending on the manufacturer and the amount of computers and features the vehicle has.

Remove the negative battery cable from the negative battery terminal. Find the negative cable, which will be marked with a minus sign (-) and may have a black cover over it. Remove the cover, if applicable, and use a wrench to unbolt the negative cable from the terminal.