My battery drains over night - 2003 Chevy Silverado - 2500 HD - Off Road Bull Bar with Skid Plate

Hello. It's possible your vehicle's BCM (Body Control Module) was 'shorting'; 'draining' the battery overnight. You stated a fuse was removed and battery voltage increased. That may be your answer; the BCM is at fault. Good luck and keep me informed; if you want to.

A glove box light will drain a battery over night or it could be a bad diode in your alternator. Disconnect the red wire from the alternator and check with a volt meter.

That red light is on many vehicles and does not drain a battery that fast. You probably have another draw on the system. I recently had a car that the battery would go down in a few days, found out it was coming from the Onstar system malfunctioning.

Usual culprit is boot (Trunk) light.If not, try disconnecting battery and if a spark jumps as you take the lead off it shows there is a power drain. If no power drain it points to a faulty battery.

Try checking the voltage of the battery after charging and disconnecting the leads.. Batteries die if being drained too much..

I suspect that your brake light switch is not being operated by the brake pedal return. When you step on the brake pedal, the switch mounted under the dash lets the plunger out operating the lights. When the brake pedal is released the pedal returns to its rest position by a spring on the brake pedal and pushes in the plunger of the light switch turning off the brake light. Charge up the battery and observe if the lights stay on at night. If so then you have to replace the switch. (about 5 bucks at parts supplier) The Air Bag light is another issue, but would not drain the battery over night. The brake lights uses a lot of amperage and would drain the battery over night.

Have you confirmed by going out to the car at night that none of the interior lights or lighted visor lights truck or hood lights are staying on? That is by far the most common cause of a battery drain. Other less common cause is a defective alternator rectifier diode Disconnect the battery overnight as well to confirm you don't have a shorted battery cell, that to will run the battery down, it is called an internal drain. Also make sure the top of the battery is clean of any acid.

the ups batteries are totaly drained,.

One by one, disconnect the fuses until you see no change on a volt/ohm meter connected to the battery with the engine not running.

have the alternator checked it could test good and still be bad but it can also drain the battery 9 times out of 10 its the alternator thats draining the battery