Hi guys

What should the amp gauge be reading when installed in a 12 volt car? At idle and when operating?

Assuming the gauge is -30amp to +30 amp.

Regards
Greg

no easy answer for this one. it depends where it is installed in circuit, whether the battery is discharged and needing a good recharge, and whether the main loads are switched on, such as head lights etc.

You need to be confident that it is installed in the right spot and have a good understanding of the circuit to make full sense of an amp meter. If its all working properly with a fully charged battery I would expect the current flow to always be charging if you have an alternator, and if you have generator I would expect slight discharge (2 to 3 amps) at idle. above idle to be charging at around 5 amps for both alternator and generator.

Better off having a voltmeter actually.

Thanks mate, I'm planning on having a Voltmeter as well.

Regards
Greg