a switch

Hi , I want to insert an on/off switch for a 12v/30A power supply . (I will draw only 20-25 A)
I thought about a switch for the AC input , rather than finding a 30-40A switch , which is I assume rarer than a simple AC switch . But Im wondering about the AC switch specifications : How much current should it be rated for ? is 3A enough (here the power plugs are 220V) ? or should I go for 5A , or even higher ?

I also though about a switch (for the DC) that belongs to some cars (I mean 1970-80's cars) which had on/off switches for their lights and those switches were like 50-60A (but 12V) .

So which way is better ?

thanks in advance .

A 3A switch will not work, as the internal mechanics will get very hot, possibly melting it. Regardless of the switch's voltage rating, you will still want a switch rated for >30A, and one rated at 50A wouldn't be overkill.

thanks .
so even if I put a switch for the AC input , I should consider 30A + ?

At 25 amps, a 12V power supply will draw roughly 12V * 25A / 0.8, or ~375 watts. If you have 220VAC, the AC current will be 375W / 220V, or 1.7 amps; So yes, you could use a 250V, 3A switch if it is connected to the AC side of the power supply.

thanks !