After time and miles, the wire connections on that ammeter would loosen, corrode and eventually burn, adding resistance to the circuit between the battery and the alternator.
(the wire connections on that ammeter; would loosen; T:After time and miles) (the wire connections on that ammeter; corrode; T:After time and miles) (the wire connections on that ammeter; burn; T:After time and miles; T:eventually)
the wire connections on that ammeter the wire connections on that ammeter the wire connections on that ammeter
would loosen corrode burn
T:After time and miles
T:After time and miles
T:After time and miles T:eventually