Instrument panel Light dim issue Valiant 1965

Hello folks, I need your help to figure out what might be going on with my 1965 Valiant.
I replaced the 3 bulbs that light up the instrument panel — I removed the original bulbs and installed LED ones. Everything was fine up to that point.

The problem starts when I turn the headlight switch knob to the left to turn on the interior courtesy light — at that point, a short occurs and blows the fuse.
I installed a new headlight switch, but the problem remains: the fuse blows when turning the dimmer on the switch.
I reinstalled the original bulbs (no more LEDs), but the problem continues.

I also noticed that the fuel and temperature gauges stopped working.
I checked the wiring, and everything seems fine at first glance.

Any ideas what could be causing this issue?