Finally got a C10

[Warrens69GMC]

Originally Posted by AussieinNC

Welcome aboard!

Nice to see a good save...

Assuming the battery is good...

The alternator diodes if faulty will cause a drain on the battery,,,,to check it, remove and insulate the wire loop connector and leave the battery connected overnight....if battery does not discharge replace the alternator...

You could also place an amp meter between the positive terminal and the lead and measure the current draw...dont try to start, and have the ignition and all lights etc turned off...post your results,,,

Based on the sketchy wiring and the fact he has a long water pump installation with internally regulated alternator, I could almost bet the truck still has the external voltage regulator in place.