We are a team of ASE certified mechanics who have created this battery draw
or dead overnight guide to help you save money by walking you through what to
look for first. A drain in the electrical system is called a
What Goes Wrong?
system can be complex with many relays, computers and switches. When one of these
items malfunctions it can cause an electrical draw which creates a battery drain. If
the battery warning light has come on prior to the problem then the battery should be okay and the
alternator has failed.
What Does It Cost to Fix?
Electrical draws can be tricky because the problem can be found in five
minutes or four hours depending on the severity of the issue and the honesty of
the repair shop.
Lets Jump In!
We'll go over the easy stuff and then escalate to the more difficult issues.
The most common problem for a battery to be dead in the morning or after
the car has been sitting for a time is a weak battery. To confirm this issue
charge the battery, then use this battery load
test guide which is easy because there is no tools or equipment needed.
If the battery fails the load test
it will need to be replaced. A sure sign the battery is bad is a sulfur
or rotten egg like smell. A battery will typically last between 3 to 4 years in most cases, if the battery is okay please
The ignition switch will cut the power to many of the vehicle's
electrical circuits. There are several "live" electrical circuits that
bypass the ignition switch which draw electrical power when the key is off
which is what we will concentrate on, these checks are quick and easy to do.
Inspect the glove box light which is controlled by a small pin switch inside
the box door frame. If this switch malfunctions or is misaligned it will
allow the light to stay on draining the battery. This can be sometimes tough
to see in the bright light of day so it's best to check this during the
evening time. Look for light inside the glove box through the small cracks
in and around the box door. If the light is on, open and inspect the light
switch to replace if needed, or make minor adjustments to help it work correctly and
turn the light off. This can be applied to the trunk light as well. Pop the
trunk open to observe the light, then slowly close the lid while watching
the light through a small opening near the rear of the trunk lid, the light
should go off. If the light stays on, replace or adjust the pin control
switch or trunk latch.
Check the cigarette lighters in both front and rear passenger compartments to see if the lighter itself is stuck down which is usually accompanied by
a fair amount of heat, pull the lighter upward to stop the electrical draw, in
this case the lighter has gone bad and needs replacement.
When you shut the ignition key off the radio turns off as well, this is not true
for the CD player and changer. If a CD gets stuck in the load or eject position
it will continue to work the small motor inside the player while draining the
electrical system. With the key off listen closely to the
player, if you hear a motor running a CD is stuck. Try to work the CD either in
or out using a small tweezers or flat blade screwdriver.
If you cannot retrieve the CD, pull out the radio fuse until you can replace the
unit or have it repaired, this will stop the battery draw.
The door lock switch is constantly hot or live with electrical power. Sometimes
the control switch will get gummed up with dirt or soda which makes the switch
stick in the lock or unlock position. This will force the lock actuator in the
door to stay on which will draw the battery down. Inspect the lock switch to make sure it
returns to its neutral position. If this switch is broken or permanently stuck,
replacement is required.
The side view mirror switch continues to get power after the ignition switch is
off. This switch like other switches can get gummed up from grime and soda which
can hold the switch on forcing the motor to draw power. Check the switch
operation to ensure that it returns to its neutral position. If this switch is
broken or stuck it will need to be replaced.
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. To check for this condition observe the operation of the seat control switch
if it doesn't return to it's neutral position or is sticking in one position
replace the seat switch with
a new part which you can get from Amazon or the dealership.
A vanity mirror located in the passenger or driver's side sun visor has
a light in most cases that can stick on. To check for this problem move the
visor slightly downward to observe a light, if the light is still on in the up
position pull the visor down to inspect the small pin
switch and repair or replace as needed.
Battery Draw Video Repair
We feature additional problems below
Heat Accompanies a Battery Draw
When a component is left on for extended periods of time it will heat up.
This can be due to a bad sensor, sticking relay or a failed computer, also a low
hum such as a fuel pump or ticking such as a
HVAC blend door actuator can be
a clue as well. Start in a quiet place with the vehicle cold and the battery
A control relay is a small electrical component that turns on and off
larger items such as a fuel pump or an air conditioning compressor. When a
relay goes bad they can "stick" causing the component to stay on even
when the key is off. Locate the under hood and interior fuse and relay
panels and remove their covers. Next, touch each relay to check for heat, if a
relay is found remove and replace it with a new relay.
Check for warm components such as the alternator, air conditioner
compressor clutch and electric steering rack motor (if
equipped). Locate the alternator and feel it
with your hand to check for warmth, if the alternator is warm with a possible burning
smell there is an internal short and the
alternator must be replaced.
An air conditioner clutch is common to create a battery draw due to a
stuck relay, to see if this is your problem place your hand on the front of the compressor to check
A steering rack is powered by an electric motor which is controlled by a
relay or module, either way it should be cool to the touch.
Listen to the vehicle by sitting inside, lift the hood and trunk and try to hear
anything that might be left on indicated by a hum or light ticking. In this case the
ABS control module was
stuck on creating a low hum and needed to be replaced.
The Powertrain Control Module (PCM) Body Control Module (BCM) or
Security Module can internally short circuit which can
cause various electrical systems in the car to stay "live" which creates an
electrical draw. This problem can be checked by locating the fuse of the systems
and removing them or removing the controllers altogether. If the vehicle starts
the next morning you have found the problem. Also a
(controller area network) will sometimes detect a malfunctioning computer.
If you have completed this guide and still can't find the cause of the
battery drain, a manual draw check of the electrical system will need to be
performed. With the ignition key in the off position and the doors closed
(driver's side window down) wait 15 minutes, then disconnect the battery
cable on the negative side, (Note: A fifteen 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 light up 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.
An alternative method is to use a voltmeter to perform a manual draw
test. With the ignition key in the off
position and the doors closed (driver's side window down) disconnect the battery
cable on the negative side. Set your voltmeter on the DC amp
scale, then attach the red lead to the negative battery post. Attach the black
lead to the battery negative cable. Use a small jumper wire along side of the
voltmeter and wait for 15 minutes to allow the modules to go to sleep. Then
remove the small jumper wire leaving just the voltmeter. Then look at your
reading, it should be about 50 to 75 milliamps which is considered a normal draw
to keep the modules backup systems charged.
If the draw is higher than that, then start removing the fuses one by one until
the draw drops to the normal levels. Once you find the fuse, you will need to
look for a power distribution wiring diagram that will show what components are
fused on that circuit. Install the fuse and go to each component on that circuit and
disconnect them one at a time until the draw drops to the normal range. At
this point, you have found the draw. Replace the component and recheck the draw
to confirm your repair.