Radio heater all work till I turn the key then they go out?

the amplifier..where is it located on my car?

I've tried disconnecting the battery but no luck.

Difficulty starting, but not consistent.

The lack of concern for other people and the desire to help others is appartently missing here. This is why I never do this. I am completely embarrased for asking for help. What was I thinking.

The can I used to recharge it was 1/2 full. Could it still need more. And How do I know.