12.3 amps is a bad battery , 500 amps is good, but you meant voltssure. (by the way sir your battery is discharged, gets forgot?)
12.3 volts rested is a discharged,state ambient temp and can tell by how much using SOC tables.try jumper cables, try a fully charged battery, 12.6v is fully charged at room temp, rested. barrow a charged battery for friends car. State of charge.. at room temp.12.3 is 50% charged,the shops dont tell you that, just GOOD battery, bad,its your job to charge, it then when cars starts, the alternator takes over, 100%the reason you are not going good ,is because no voltmeter in hand. For SURE.guessing dont work here, only tests and measurements.1; can you try turning the cars crankshaft by hand.?siezed, bingo2: can you hot wire the soleniod small pin to the outside big pinlike here,
http://www.fixkick.com/nocrank.html#test1if the battery is weak, this test is useless. on all cars.if it works then the key line is deadif not the battery ,or cables or starter is bad.there are 3 parts to a starter, i repeat, the battery (charged) the cables and the starter.engine turns by hand. yes.those are all facts. another tack.voltmeter across battery lugs.crank 0v bad battery or shorted or siezed motor.12v, starter dead open circuit.10v typical with fast cranking.you can see this in 2 dimensions. here.time is the horizontal axis.
http://www.fixkick.com/Charging/start-voltage-scope.GIFif living in Nunavut city, cancel my help.new tables.