A car battery is used to store
electrical power in reserve to be used when the car engine is started. Several conditions
can occur that will cause a battery to lose its charge overnight. There are several
"live" electrical circuits 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 you will need to start the engine by
jump starting
or charging the battery using a battery charger. Once the engine is running
test the alternator in the
charging system. If the alternator fails, replace it with a new or rebuilt unit
and re-test system, if the alternator tests ok proceed to the next step. Follow
the troubleshooting guide below:
Car Battery
Step 1 - This first test is simple but you would be surprised
at how many people simply leave their
headlights on overnight. If
the battery is dead check the headlight control switch. If the switch is in the
on position turn the switch off and jump start or charge the battery. The battery
should re-gain its state of charge after about 15 minutes of driving and your problem
will solved. If headlight switch is off proceed to next step.
Step 2 - Inspect the interior illumination lights (dome light)
when all the doors are shut the interior lights should go off. If the lights stay
on check the headlight interior light bypass switch located at the
headlight switch. This switch
is designed to illuminate the interior lights indefinitely when the doors are closed
and is used when people are left inside the car and need light for a particular
reason. To check the headlight interior light bypass switch turn the headlight control
knob fully right then left, you should feel a small bump in the operation letting
you know when the switch is activated. Deactivate the switch and re-test dome light
operation.
Some cars have a delay sentinel that will leave the interior light illuminated
for a preset amount of time and is used for safety reasons. If this delay mechanism
fails it can leave the interior light on draining the battery. If this is the case
the interior light delay sentinel or
Body Control Module
will need to be replaced. If all tests okay proceed to next step.
Step 3 - Inspect the
car stereo tape deck or CD player,
sometimes a tape or CD will get stuck in the player either loading or ejecting causing
the motor inside the tape deck to stop. This small motor can draw enough electrical
power to drain the battery overnight. If a tape or CD is stuck in the player try
using a small flat bladed screwdriver or small tweezers to remove the culprit. If
the stuck tape or CD will not come out. Remove the player and disconnect the unit.
Once the unit has been removed either replace the player or send it to a stereo
repair shop and reinstall when repaired. If player tests okay proceed to next step.
Step 4 - Inspect the glove box illumination light, in most cases
this light is controlled by a small pin switch. If this switch malfunctions or is
misaligned it will allow the glove box light to stay on draining the battery down
overnight. To check for this condition look for the light inside the glove box through
the small cracks in the glove box door. If this light is illuminated when the glove
box door is shut replace or readjust the switch to operate properly and recheck
light operation. If it tests okay proceed to next step.
Step 5 - Inspect the trunk illumination light, in most cases
this light is controlled by a small pin or a mercury level switch. To test the trunk
light operation observe the light as you close the trunk lid, the light should go
off when the trunk lid is nearly shut. If the light doesn't go off replace or readjust
the switch and recheck operation. If it tests ok proceed to next step.
Step 6 - Inspect the hood (covers the engine) illumination light,
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, 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. If it tests okay proceed to
next step.
Step 7 - Inspect the cigarette lighter in both front and rear
passenger compartments, remove the lighter unit and look down inside the light socket.
You are looking for debris that can cause an electrical draw like a penny or a gum
wrapper. Anything that can cause an electrical draw will drain the battery power.
If debris is found remove it with a small pair of tweezers. (Note: sometimes when
inserting tweezers or removing debris from the cigarette lighter a fuse can blow,
if so replace the fuse with new after the debris has been removed) If the lighter
is okay proceed to next step.
Step 8 - Inspect the electric seat control switch, 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.
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. What this
means is you will be checking the electrical draw the battery has on it when the
car is locked up, with the key in the "off" position". First open the hood and disable
the under hood illumination light, if equipped. Next, with the key off and the doors
locked wait 15 minutes, then disconnect the battery cable on the negative side.
(The 15 minute wait allows the computers to go into "sleep mode" and shuts down
all electrical).
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 this electrical
draw start removing fuses one at a time. When the test light goes out the circuit
in question has been located. You will need a car repair manual to identify all
accessories in a particular circuit, repair as needed and re-check system.
If further technical assistance is needed, our certified car repair technicians
are ready to answer your car questions.
Related Car Repair Information
