On Fri, 31 Jan 2014 06:59:53 +0000, Andy Burns wrote:

Does the phone detect the charger as capable of delivering high current?
If so, it should display "Charging A/C" instead of "Charging USB"

I checked what the phone says when it's on the 2.1 Amp
cigarette lighter charger, and, interestingly, it does
say "Charging (AC)" (even though that 2.1 Amp figure
has the word "iPad" next to it on the adapter).

So, had it said "Charging (USB)", that would have been
my problem - since it actually says "Charging (AC)", we
know that's not the problem.

I'm think I will need to sacrifice a USB cable, by cutting
it in half, and then checking the wires (or buying a test
fixture that allows me to hook an ammeter in series).