I installed an alpine double din iva-w203 p1 and then i accidentally touched the hot wire to the negative wire while trying to screwin the toggle switch and then i tried putting in three different head units including my stock one and it wont turn on HELP!!!! i check all my fuses and none are blown so i dont know what to do please if someone could help me

hmmm yeah i would have guessed fuse. next i would verify that power is making it to the head unit, check the power with a multimeter (if u dont have one relatively cheap at radio shack). if other head units arnt working either, its probably the power, wich means u might have missed a fuse somewhere... but definatly try to verify good power.

It has to be a fuse bro. If none of them turn on but your car still does, its a fuse. They don't have to appear exploded inside to be bad.

the same thing happened to me (except i have no idea how it happened) but with my radio i couldn't get the screen to turn on except when i needed to open it or close it, but then the screen would turn back off. so then i took it back and got it raplace for a new HU since it was only a week old and still nothing. Then I swapped it back for the stock radio and nothing happened either. Checked my fuses and had a blown fuse swapped it for a new one and it worked perfectly! it's gotta be a fuse for it to not work with any HU. If you don't have one already, invest in a multimeter because you can check if your fuses work with that.

it's a fuse and you will find it in the fuse box next to the battery, standing infront of the car you will find a 7.5 (red colored) fuse that is by it's self at the top.