Help! Head unit sparks on install

[Stripes]

The car is a 240sx.I'm installing my pioneer head unit and when I start to screw it to the dash i get sparks coming from the screws. I just used this head unit the other day and it worked, and I don't remember having a ground wire anywhere when I last took it out. Should a screw on the side of the unit be grounded?Sorry if this sounds confusing, I'm not good at explaining problems with stereos.Thanks in advance!

[Looneybomber]

Umm, no, headunits do not ground directly from them, there's a ground wire out the back that then goes to some chassis ground. Check to make sure your ground is hooked up and also check to see how the power wire is hooked up.

[Broadfield]

The car is a 240sx.I'm installing my pioneer head unit and when I start to screw it to the dash i get sparks coming from the screws. I just used this head unit the other day and it worked, and I don't remember having a ground wire anywhere when I last took it out. Should a screw on the side of the unit be grounded?Sorry if this sounds confusing, I'm not good at explaining problems with stereos.Thanks in advance!

It's sparking because you don't have the ground wire on the back hooked up like Looney said. The radio is trying to complete the circuit through the chassis of the radio..... and that's why you are getting sparks on the screws. The metal chassis of the radio is mounted to a metal bracket, which in turn mounts to metal in the dash with metal screws. You do the math.