Number 9 fuse blowing and dimmer light not working

[RoseburgSierra]

First time doing this..
One day the instrument panel lights controlled by the dimmer when out. So I decided to buy a another headlight dimmer switch. It came and I installed it. Other functions are back working just not the lights controlled by the dimmer. Checking the fuses I saw #9 was blown, so I changed it twice and it blew each time when I turn the headlight switch to the next position..anyone have any ideas? Ps #14 fuse is fine

 

[texas tough]

likely a short in the trailer plug wire harness that is hooked into the headlights., when dash lights wont work, taillight wont either. if that fuse blows.