Can someone explain the 70s charging system?

[Big_John]

What effect has a Battery which wont hold a charge that good anymore on the running system when a load kicks on?

It kinda depends on what is wrong with the battery. It may limit the charging voltage and that might be your problem.

 

[Knebel]

hm. Here is something... when i turn the key, there is some load on the battery, approximately... 30amps. I see 11.7volts (should be dead right?), it cranks over strong and when cranking I see 10.5 - 10.8v. While running, I see somwhere 13.8 to 14.5v, my fan kicks on and the charging system dips as low as 12v....then slowly climbs to about a steady 12.5v at an idle. I am trying to figure out another idle "issue" with my efi (wont idle higher than 800 in drive). I know my voltage goes into the 13v range at 900rpm, so maybe i just need a smaller pulley on my alternator?

EDIT: I am mainly trying to figure out if there is even an issue.... thats why i was asking how the system works.

 

[Big_John]

I am mainly trying to figure out if there is even an issue

Well.. If the car starts and everything runs, I'd say it's all OK. There will always be some fluctuations and if you have a weak battery, that can be worse.

 

[Knebel]

haha yeah I guess I am just paranoid when the voltage goes down so much that it wont charge the battery... I mean... I have fixed a lot of wires and actually installed a 4ga OFC charging wire today from alternator stud to battery. I think the 8ga copper clad alu might have been too weak...