No electrical unless engine is running. Has a new battery, any ideas?

[Plazzmo]

A few days ago, my 1984 started to have some electrical issues. Unless the engine is running, none of the electronics have power, and I have to jump start it every time I want to drive it anywhere. I first noticed the lack of electrical power after I took out the aftermarket radio the previous owner had installed, (not sure if removing the radio could've caused some sort of electrical circuit that's draining the battery or something?). There are a lot of loose wires around where the radio used to be, a lot have exposed ends.

It runs ok after a jump start and the electronics work fine while the engine is running. The previous owner said the battery is only a few months old so I don't think that's the problem unless it's defective, or if he was lying but it looks pretty new. Any help would be awesome. Thanks

 

[fourwd1]

Start by measuring the battery voltage when the engine is off vs running.

 

[RAD4Runner]

Possible bad battery and/or connnections

...Unless the engine is running, none of the electronics have power, and I have to jump start it every time I want to drive it anywhere. ...There are a lot of loose wires around where the radio used to be, a lot have exposed ends.

Whether they're causing your problem or not, they might cause problems later, and leaving exposed wires is always bad practice.

It runs ok after a jump start and the electronics work fine while the engine is running. The previous owner said the battery is only a few months old so I don't think that's the problem unless it's defective, or if he was lying Thanks

Quite Possibly dead weak battery or battery is weak and not enough power is getting to the electronics because of bad connection between battery and electronics, especially circuit between battery and ignition switch (including, fusible links, fuses). Load drops battery voltage, AND corrosion in connectors causes too much voltage drop across connection, so there's not enough voltage to run electronics or start engine. When you jump start, battery voltage remains high enough to start engine, and run alternator which keeps voltage up even after you disconnect jumping vehicle.

Start by measuring the battery voltage when the engine is off vs running.

+1. If battery voltage (alternator output really) while engine is running is significantly higher than with voltage with engine off, Most likely P.O lied

Looks can be deceiving, Even if connection looks clean on the outside, the interface (encircled in orange below) between battery terminal and could have corrosion that can cause problems. (First-hand experience)

 

[4runnertank]

It honestly just sounds like a bad battery. It's really easy to fry a battery, no matter how old it is. I accidentally sparked mine a few months ago and it was DONE. Check it's voltage and then we'll go to the next step at figuring it out