[Halscion]

Okay, maybe I'm exaggerating a little, but the frustration is starting to get to me.
Here's a brief outline of what I've done and the problem.
Installed a Profile 4 channel amp under the passenger seat, Polk Audio component 5.25 speakers in the front, Pioneer 5.25 2-way in the back, Infinity Basslink mounted in the hatch.

I finish the install, put all the panels back in and take a listen. The sound is horrible. Background hiss, engine whine, pops & crackles, and momentary loss of sound when shifting or going over random bumps in the road.
To remedy this I do the following: replace the 20 feet of RCA cables with higher quality and shorter Monster cable, take the head unit ground wire and ground it at the passenger seat bolt (same place as the amp), turn down the gain, place some insulating rubber against the metal spring under the seat that was contacting the metal case of the amp. Bingo. The hiss, whine, and pops are gone.

Then I notice a huge problem.
I have NO dashboard lights! The backlighting for the speedometer, tach, fuel gauge, climate control, radio controls... all of it completely dark. The stereo works and the climate controls also work fine and the actual display for the radio and the climate control are lit up, but the backlighting behind the controls is dark.
I can't drive at night, not being able to see the speed or the tach.

Everything was working fine until I clipped the head unit ground wire and spliced it to the passenger seat bolt. I just want to make sure that what I clipped was actually the head unit ground wire. It is the dark green wire next to the grey (ACC) and the blue (battery+) wires. These 3 wires when directly viewing the back of the head unit are the furthest to the right. Did I pick the right wire? I tried reconnecting the green wire, but that didn't do anything.

Another possibility is that I might have inadvertently pulled something out while rerouting/pulling/tugging the new RCA cables, but I couldn't find anything suspicious or loose.

Or could I have blown a fuse?
Is there another really simple and obvious explanation that I'm missing?

Aaaaaaaaaaaahhhhhhhhh. I'm going to run amok.


EDIT: I noticed that there was a rather large black "plug in" type wire to the right of the wiring harnesses at the back of the head unit. Anyone know what this is? Could this be the real ground wire?

 

[Halscion]

Alpman,

Thanks for the tips. I had a suspicion I cut the wrong wire. I should have double checked the schematics. BTW, according to the Scion wiring diagram the pin 7 wire is brown. I'll take a look later and see how it goes and what color is actually there.

The seat bolt seems to work fine as a ground, I used sand paper and scraped off all the paint to bare metal at all contact points to the ground wire(s).

Now I seem to have eliminated 90% of pops, whine, or crackle. BUT I still have the problem of the sound cutting out for an instant when I shift. It's like when you play the stereo and then turn the headlights on, for an instant, the current drain cuts out the sound. This same thing happens when I shift, but not all the time, just occasionally. This one has me stumped. I've routed the RCA cables from behind the head unit through the center console (and parallel to the shifter mechanism). Speaker wires and antenna remote wire also are all bundled together along the same path and emerge through the carpet and under the passenger seat.
Any idea of what might be going on?

Thanks again.

BTW, do you know where the relevant fuse(s) is/are located?

 

[Halscion]

Dashboard lights are back on after changing a 7.5amp fuse and rewiring the previously cut green wire. Yes, it is a stock deck. The turn on lead is spliced into the grey ACC wire (pin #3).

I'm still having problems with the sound cutting on some shifts. I wonder if there might be a static charge that is building up in the shifting mechanism that is occasionally discharging into the nearby wiring?

BTW pin#7 wire is brown.

 

[Halscion]

Thanks for the response.
All splices were soldered and taped.
Looks like I've got some time on my hand to figure out this problem. Aside from that, the system sounds great!