Q: New battery goin dead over nite

Hi there. To check to see if something is still on with the key on, remove the ground cable to the battery and put a digital volt ohm meter (DVOM) on the cable and onto the battery negative post. With the key in the off position, there should be no power, however, if something was to be active, there would be power. If the meter shows up with a small 0.2 voltage, then that is normal. If the voltage is 1 volt or more, then you have a parasitic draw (something staying live draining the battery with no way of charging it).

For the battery to drain overnight, there has to be a voltage of 5 volts or more present. The way to check this is remove one component at a time. For your radio that is not working, remove the power wire to the radio and if the voltage drops to 0, then the radio is the problem. If the radio is not the problem, continue unplugging one thing at a time until the meter reads 0. Then fix that part to keep your battery from draining. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic, that can assist you with your battery issue.