I've taken it off the car and connected it to the charger but the amp gauge flicks up to number five on the gauge which is the highest bit, it stays there for a second then flicks down to 0 for a second then back up.

Now last time i used it it didn't do this sooo whats going on now, i'm wondering as the battery is severaly discharged [3v] it's giving max input but to prevent over-heating it's flicking back to zero every couple of seconds? does that sound right?

it's quite a old battery charger and i don't have the instructions