The truck leaks voltage overnight. It starts really weak, but quickly charges over 14V, and the battteries are less then 2 years old. I have a stereo that is plugged directly into a live wire. I wouldn't think that leaks, but maybe?

Whats the best way to check for power leaks?

 

An amp meter , maybe a good one , because the cheaper ones do not work as with low draws .
But load test the batteries also , then look inside the cells to see electrolyte levels , replace with distilled water .
If you do find a draw , then pull & replace fuses one at a time till you find the draw , if it has one , glove box lights are you that you may not notice , if the light is on with the door closed .
Then testing the alternator , it can have a drain in it also .

 

Disconnect the negative post on the battery(s) untill the power goes out. Use a multi-meter set on milli-amps, and hold one lead to the negative battery post, and the other to the negative battery cable. Essentially completing the circuit through your meter. If the meter goes into negative numbers or hits the "zero" peg really hard, swap the meter leads around. I can't remember which one goes to which one, but it's obvious if you have it backwards. It won't hurt it.

Make sure everything on the truck is shut off including the dome light and the underhood light. Key in ignition dinger, etc.


You'll be able to see how many milli-amps you're burning when you're not supposed to be. Start pulling fuses one at a time untill you see the meter drop significantly. You've just found the circuit that your drain is on.

This saves a lot of time chasing power loss.

 

Have your batteries tested at wally world free. One may be down.
You need a little more instructions. Before diconnecting the second battery, hold the test lead to bottom of post and to cable you are disconnecting. Otherwise the computers power down and power back up (memory) when hook multimeter into circuit. Sometimes gives a false reading after total disconnect. Make sure doors are closed and lights timed out. JMHO

 

If you don't have a meter you can can substitute a 12 volt test light.
Follow same instructions as Yota explained except the juice flows though the bulb instead of the meter. Brighter light equals more amp draw.