Percolation? Heat soak? Don't drive during summer??

Mattax said

With a fully recharged battery and a working alternator, no current flows through the ammeter.

More charging with rpm means one of two things.
1. Battery is extremely low on charge or is damaged.
2. Voltage isn't properly regulated so its going up with rpm.
Fix this because it will cause all sorts of problems, some of them potentially disasterous.

Click to expand...

It can also mean there's something spliced into the battery side of the connection, and the 'charge' indication is current flowing to whatever that is.

In any event, @Mattax is right - it's a situation which can result in a fire. It would be wise to figure out the cause, correct it, and then do an ammeter bypass and/or a 'wire around' with a heavy gauge wire from the alternator to the main battery splice.