Mechanics

Battery Goes Dead Overnight

Easy step by step repair guide on how to fix an automotive battery that goes dead overnight, steps are presented in order of popularity, this article pertains to most vehicles.

Difficulty Scale: 3 of 10

Before you begin park the car on level ground, in park with the emergency brake "ON", using basic tools wearing protective eyewear and gloves.

Step 1 - If the alternator has failed it will allow the battery to go dead. Visit - Alternator testing


Alternator

Step 2 - Inspect the interior illumination lights (dome light) when all doors are closed completely, the interior lights should turn off. If the lights stay on check the headlight interior light bypass switch located at the headlight switch, you should feel a small bump in the operation while rotating the thumb wheel informing you know when the switch is activated, also check the door pin switch (light switch) adjustments. (Note: Some door latch designs include the door light switch.)


Interior Light "ON"

Step 3 - Inspect the car stereo CD player, sometime a CD can get stuck in the player either loading or ejecting causing the motor inside the tape deck to keep running overnight.


Stuck CD

Step 4 - Inspect the glove box light, in most cases this light is controlled by a small pin switch inside the glove box door frame, if this switch malfunctions or is misaligned it will allow the glove box light to stay on draining the battery down overnight, check for this condition in darkness while looking for light inside the glove box through the small cracks in and around the glove box door.


Glove Box Light "ON"

Step 5 - Inspect the under hood and truck lights, in most cases this light is controlled by a small pin or a mercury level switch. To test the hood light operation observe the light as you close the hood or trunk, the light should go off when the hood is nearly shut. If the light doesn't go off replace or readjust the switch and recheck operation.


Under Hood and Truck Lights

Step 6 - Inspect the cigarette lighter in both front and rear passenger compartments, remove the lighter unit and look down inside the lighter socket checking for debris that can cause an electrical draw like a penny or an aluminum gum wrapper which can cause an electrical draw will drain the battery power. If debris is found remove it with a small pair of plastic tweezers. (Note: sometimes when inserting metal tweezers when removing debris from the cigarette lighter a fuse can blow so use caution.)


Cigarette Lighter

Step 7 - Inspect the electric seat control switches, this switch can become sticky or weak allowing the switch to stay engaged forcing the seat motor to draw power from the battery until dead. To check for this condition observe the operation of the seat control switch if it does not return the neutral position or is sticking in one position replace the switch with new and recheck.


Seat Control Switch

Step 8 - If headlights are left "ON" overnight the battery will be dead, check the headlight control switch. If the switch is in the "ON" position turn the switch off, jump start or charge the battery. The battery should re-gain its state of charge after about 15 minutes of driving.


Headlight Switch "ON"

Step 9 - If no other electrical accessory is causing the battery to drain overnight, a manual draw check of the electrical system will need to be performed. Open the hood and disable the under hood illumination light, if equipped. With the key in the "OFF" position and the doors closed (drivers side window down) wait 15 minutes, then disconnect the battery cable on the negative side. (Note: A 15 minute wait time allows the computers to go into "sleep mode" which shuts down most electrical systems.)

Attach a test light between the negative battery cable end, and the negative battery terminal, the test light should illuminate dimly or not at all. If the test light is "ON" brightly there is a strong electrical draw in the system. To locate the draw start removing fuses one at a time, when the test light goes out the circuit in question has been located. Identify all accessories in a particular circuit by using a wiring schematic. Google Images

Helpful Information

A battery is used to store electrical power which is used when the ignition key is turned to the "ON" position. Several conditions can occur that will cause a battery to lose its charge overnight. There are several "live" electrical circuits that bypass the ignition switch that can draw electrical power from the battery when the key is in the off position. As a battery ages it loses its ability to hold a charge, as a rule of thumb a battery will last about three to four years. If the battery is fairly new but dead, you will need to jump start the engine which will charge the battery. Visit - Jump Start

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-05-08)