s14 stereo problem

[myles89]

I feel like such a noob asking this question.

I've installed radios before but for some reason cant get this one to work.
i have a 95 s14 and when i bought the car 3 years ago it had a pioneer head unit. I decided to swap the pioneer for a sony headunit i salvaged from my other s14. I wired it up and for some reason nothing worked. It never got power or lit up or anything. I decided i didnt want the hassle so i put the pioneer back in and it worked fine. I sold the sony and the guy said it worked great. I've had the pioneer in there for nearly three years and it finally decided to go out.
I bought another sony headunit from a friend of mine and wired it up and i have the same problem. no power at all but i know everything is wired up correctly. Yes the antenna is connected. Yes i've bolted it into the bracket for additional grounding.

so i have two questions:
1st i assumed the stock amps had been bypassed by the previous owner because the pioneer stereo worked fine. is there a way to double check to make sure this happened.

2nd my harness adaptor coming from the car has 2 black wires one marked chassis ground one marked amp ground. I thought 240s were grounded threw the antenna wire so im at a loss for what these wires are.


sorry for such a long question i just wanted to be sure to give all the info to anyone reading this.

thanks for any help you got.