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Discussion Starter · #1 ·
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?
 

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The green wire you cut would happen to be the illumination (+) wire. You probably blew the parking light fuse. Reconnect that wire to the radio and check/replace your fuse. The wire you are looking for is in pin #7. It should be a white wire with a black stripe. Run your ground trace wire to this point. Looking at the back side of the harness, it should look like the illustration on this page:

http://www.carstereohelp.net/wireharness_Toyota3.htm

The radio pictured is not the Scion/Pioneer radio, but the pin-out is the same for the main connector. Remember, the pin-out is as if you were looking at the back side of the harness. From the front side it will be a mirror image.

Also, it is best NOT to use a seat bolt for your amp ground. There is alot of paint/undercoating, etc in the threads of the seat bolt and will not make for a good ground point. Use a self-tapping screw with star washers and scrape the paint with a wire wheel brush at the seat rail for a good ground. Bad grounds can cause all kinds of problems w/ amplifiers, including engine whine and thumps/pops etc.

Good luck, hope this helped.
 

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Discussion Starter · #3 ·
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?
 

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I was going off of memory on the wire color, I may have been wrong. It is definately pin #7 though. As far as the amp cutting out while shifting, I'm not sure. Double check the cable rounting to make sure nothing is pinched. Are you still running the stock deck? You didn't mention that before. If so, where did you connect the turn-on lead for the amp?
 

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Discussion Starter · #5 ·
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.
 

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Glad I could help. The sound cutting out could be a bad connection at turn-on lead or the speaker leads. How did you make these splices...solder, butt connectors, t-taps or just wrap & tape??? I doubt it is a static issue. It could also be a bad hi-to-low adapter as well. Many of them are cheaply made and i've seen them w. bad solder juntions as well as inferior parts used causing many problems, including the ones you have described. Just giving some troubleshooting ideas...good luck!!!
 

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Discussion Starter · #7 ·
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!
 
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