Chargeing system problems

I have a cadilac 390 with a generator in my model a my problem is when I first start the engine it seems to always charge according to the volt meter then after driving awhile it seems to stop any ideas thanks

 

Could be the battery is charged and doesn't need any more help from the generator.... you using voltmeter and not a ammeter?

When it gets hot and isn't showing it is charging, pull the negative cable off of the battery while it is running and see if it is still charging.... it will die if it isn't, will keep running if it is.

 

I guess the next question is are you experiencing slow starting problems, dim headlights??

 

Also does you gauge read into the negative or just at zero. As said may be the battery is fully charged. Does the gauge move at all when you put the headlights on?

 

Battery going dead lights get dim flashers start flashing strange only other draw would be electric fan thanks

 

OK, so not just an erratic gauge, charging system problems for sure. That helps.
This is where a volt meter and a test light, battery charger would be helpful.
If you can charge the battery up, a drive to the friendly local auto repair shop to make sure bty is still good.
A battery load test is where you are supposed to start, but the battery has to be near full charge to test this way.
Once you can eliminate that the battery as the source of the problem, you're that much closer to finding the problem.
Sick batteries won't accept a charge or a very small charge. This is the symptom you are describing.
Check the battery out real good.

 

have battery charger battery charges right up almost seems to be rpm related if I start engine and start driving and keep driving seems to charge good but stop for a light or slow traffic it stops charging