Thanks for choosing JA,
It definately sounds like a battery to me, something is possible drawing power overnight.
I have heard of the factory stereo doing this, I have also heard of the glove box light switch.
Heres what to do:
1. When testing for a parasitic drain on a vehicle, an ammeter placed in series with the vehicle batter
y cable and batter
y should be used. Amperage draw is the only accurate method of determining acceptable parasitic load on the electrical system.
2. Place a shunt in series with the batter
y and batter
y cable (Note: It is advisable that batter
y power is never disconnected from the vehicle. The use of a jumper batter
y to keep the vehicle electrical system energized will eliminate problems with radio recoding, antitheft recoding and idle and transmission relearn issues). Place the ammeter in parallel with the shunt.
3. The shunt is used to carry the full electrical load of the vehicle until parasitic draw testing is started.
4. Start the vehicle and turn on and then off every electrical device and load on the vehicle.
5. Shut the vehicle off, close and lock the doors and close all windows and sunroof if equipped and then open the shunt on the batter
y. (Note: Be sure to disable any hood position or alarm switches on the hood if the hood is to be left open during testing).
6. Leave the vehicle undisturbed for a minimum of 30 minutes. This allows all onboard computers and processors to enter "sleep mode". After 30 minutes the vehicle should be at its minimum parasitic load.
7. Observe the parasitic load as indicated on the ammeter. 50 milliamps or less is the permitted parasitic load on the electrical system.
8. Should the load exceed 50 milliamps, begin pulling fuses from the fuse box one at a time until the draw drops below 50. Once it is determined which circuit the draw is on then use available wiring diagrams to locate the faulty component.
*shunt - A shunt
(aka a current shunt resistor
or an ammeter shunt
) is a high precision resistor
which can be used to measure the current flowing through a circuit. Using ohm's law we know that the voltage dropped across a resistor divided by the resistance of that resistor is equal to the current, therefore if we measure the voltage across a shunt resistor
in a circuit, we can easily calculate the current.