Help! S13 Masters! Riddle me this.

[Benston]

This started with the original KA24e in 1990 S13 coupe. The car would drive fine until you turn on the headlights then the car would try to stall out and eventually die like the battery was draining. Also, the dash lights wouldn't work unless you rev the engine. Would that be cause by an alternator that was going out or a bad diode or whatever? The ka was pulled out of the car and a n/a sr20 was put in and wired up and still it does the same thing.
It's an S14 SR20DE with the sr MAF and sr ECU and complete wiring harness. The wiring harness was wired for an s13 by the guy at the shop that I bought the motor from. After getting the sr in and ready to run i figured out i wasn't getting fuel. While dropping the gas tank I found two wires that had broken off the pump. So after soldering the wires back and checking the pump I found it did not work. I replaced the pump and remounted the gas tank. Now the car will start and run fine and idle fine for about ten minutes tops then it starts to stall out and sputter like its draining the battery still like the same thing was happening with the ka in it. Trying to stall and die when I give it gas, too. Obviously its the chassis wiring and not the motor. Right? I need any suggestions. S13 wizards I beseech thee. I live right outside of Memphis. I will pay someone to fix it if you think you know what might be causing this. Message me your number or something. Email Address. Anything. Any advice is appreciated.

[compactfean]

Sounds like to start you need to have the battery tested and alternator tested under a electrical load. let us know the results.

[blkvrtswp]

^^ This. You can take the battery in to most auto parts stores and they will test it for free. Most places no longer test alternators off the car, but the Autozone near me does. I even got a printout for both battery and alternator.

Also check the voltage when engine running across the battery terminals. Less than 12 volts means it is not charging. Things like audio start malfunctioning around 10 volts.

Make 100% sure the negative battery cable is tight & solid as a rock on the battery terminal.

Chassis wiring is unlikely to be involved unless there is a short or current draw draining your battery faster than the alternator can keep up with.

[N/A Q45]

The stock wires can and do corrode/ oxidize and you can't tell just by looking at them, I replaced most of mine for the starter, grounds and charging system because of this and a few other reason's.
You can test you battery and alt yourself, leave the battery unhooked test its voltage before you unhook it overnight and test the voltage it has after sitting for atleast 8hrs should be around 12-12.6v then if that the voltage stays within that the battery is more then likely A okay. Hook it back up, run car till it is warmmed up so everything is up to temp and working the way it should, let the car idle and check the voltage at the battery onec with no load (every thing in the car is off) should be 14-14.7ish volts then turn everything on (lights, heater on full, rear defrost ect) if it drops to less then 12.5 there's a problem in the charging system ( alt or wires/connection)