New to the forum, so bare with me if I go against any rules. I am down to learn if I do something sideways or wrong.
1991 Volvo 240. Alternator replaced, battery replaced. When I get the battery to its respected 12.4 or what have you, I start the car, and the alternator shows 14 or so volts charging.
As the time goes on there is a draw. the draw can be seen on my volt meter whether I test from the battery or the alternator, eventually draining all available power causing slowly all the lights to light up and then the car dies.

I have checked all the fuses, tested all the grounds on battery and alternator...

Stumped! It's truly not vary often with simple machines, you know spark, fuel, air sort of thing. What I am hoping is that I get humbled to the max and shown how it's an easy fix.

After a couple times of this through replacing and checking items the check engine light is on, and I have not checked to see if the code helps.

Any advice would be accepted with excitement. Thank you!

(I trust this is with the engine still running)
OK - 1991 240. Voltage at battery when running is 13.5-14 or so when first started. Then after awhile - with your words - "eventually draining all available power causing slowly all the lights to light up and then the car dies".

You have a BAD alternator, or a very bad connection (between the alternator and the battery) or the crankshaft pulley (vibration damper ) is slipping so much that the alternator is not spinning once the pulley gets hot (and expands) Easy to check for slipping with a timing light. (and I have replaced hundreds of front pulleys/vibration dampers for slipping problems, usually they will make a squealing noise - but maybe not when very loose/worn out. )

The B+ (big red wire) from the alternator goes to the starter, then to the B+ terminal on the battery.

I’ll pull the refurbished new alternator and have it checked. It’s strange to me that when I first get it it started the alternator is working at the 14 charge level, but then declines as the battery does…but it’s fairly easy anyhow to get off and on anyhow. If you have any other thoughts go ahead, though like I said before, I hope I’m humbled and it’s that easy! 😉

I’ll check the timing also, though it sounds fine so that stumps me as with timing issues I would hear that, right?

You check the timing - not because the timing (when the spark plugs fire) is off or changing -

If the outer part of the crank pulley/vibration damper is slipping on the rubber ring (in the middle of it) The timing marks will be moving (in relation to the inner hub of the pulley) as the outer part slips.

If so - the outer part can slip enough to slow the alternator to where it does not charge anymore. When the pulley gets bad enough - you can spin the outer part with your hands (once the belts are removed)

Put a white mark on the timing marks on the pulley - and see if they stay in the same place when idling

I replaced the harmonic balancer, battery, and alternator. I polished all the ground connections. Took it for a drive and ran better then ever but slowly the abs lights etc. turned on and, dead, like just then and there in a moment. Pushed it off the road and battery was dead.

help?!

A 240 uses 2 MATCHED alternator belts - do you have 2 and were they sold as a matched pair?

Where are you sourcing this alternator you are using?