Factory Rockford Fosgate Amp Integration/Bypass

NismoFire

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Smyrna, TN
My SE has the Fosgate Audio system in it, and the speakers are wired to the amp. My new head unit doesn't have the extra space for the amp, with the exception of RCA jacks.


Has anyone successfully tied the factory amp into an aftermarket head unit?


I found this..
2009-09-23_210830_2002_Xterra_Radio_diagram_w_amp_1.jpg


2009-09-23_210941_2002_Xterra_Radio_diagram_w_amp_2.jpg


2009-09-23_210955_2002_Xterra_Radio_diagram_w_amp_3.jpg




...but I can't make any sense of this stuff.
 
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drbandkgb

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They sell direct plugs for the aftermarket radios I thought


Sent from the satellite of love..
 

NismoFire

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Smyrna, TN
For the amp?? I'd like to keep it if I can. Otherwise, I'll have to make sense of that diagram and hardwire everything together & bypass the amp.
 

J Everett

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Location
Houma, LA
Damn, I wish I lived nearer to you; we could wire stereos to the amps in both our trucks. I know how to do it, but I just haven't gotten around to it yet. I know Metra has a wiring harness (for the second gen, at least) that allows you to run signal from your RCA outs on an aftermarket head unit directly in to the amp's preexisting inputs from the factory head unit.

You have a first gen, right? I'm going to subscribe to this thread and if you have any questions I'll be happy to answer them. What you want to do is a lot easier than you think, so don't sweat it!


EDIT: Metra makes the harness to use the factory Rockford Fosgate amp with an aftermarket head unit in both first and second generation Xterras.
 
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J Everett

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Houma, LA
Part number for the harness, perhaps?
There's a link to it in the "This is the harness you need" bit above, but I just realized that links don't seem to show up very brightly on this site. Gonna post in the site problems thread about this.
Anyway, it's:
Metra part #70-7551
 
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NismoFire

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I knew there was, but I couldn't seem to find the one with the RCAs.


Thanks J!! Rep for you when I get on the computer.
 

NismoFire

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Got the harness ordered, will be here by Wednesday.


There are actually two harnesses/sets with a total of 4 RCA plugs...I've only got 2 RCA plugs on my head unit...
 

NismoFire

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Smyrna, TN
Alright, JE...here's where I'm at now..

6656845723_793b6e63d8_b.jpg



I have a few leftovers on the harnesses...

Orange- Illumination
Black- Ground (obviously)
Blue- Power Antenna (n/a)

Then on the other harness I have:
Black/White- Amp Ground



I'm not worried about the illumination or the power antenna, because the harness for the head unit doesn't have either. The one I AM worried about is the Amp Ground...do I need to connect that to the head unit ground and run them both to the chassis or leave it alone?
 

J Everett

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Founding Member
Location
Houma, LA
OK. Here's what I can figure out as for the Blk/wht Amp ground wire. The amplifier is already grounded to the vehicle near where it's located. As far as I can tell from the wiring diagram, there's no connection between the stereo ground and the amp ground. So, you should be able to tape it off and leave it unused.

The black ground wire on the Metra harness should be connected to the black ground wire on the new stereo harness. And those spade connections need to be wrapped in tape or heat shrink tubes. Something to keep them from possibly touching metal behind the dash or each other and arcing off and causing a fire.
 

NismoFire

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Roger that.


Now here comes the fun part...putting all the OEM plugs in to the Metra plugs.


Once I figure this out, I'll do a proper write up. This thread is too bouncy and unorganized to count as a decent write up. LoL.
 

NismoFire

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Smyrna, TN
I'm back...got everything plugged in, and the only thing coming out of my speakers (with FM or CD) is nothing but BASS. And I mean BASS. Holy crap. Everything else sounds very muffled and muted. I checked all my connections, everything seems to line up right.

Here are the harnesses coming out of the dash.

The two harnesses on the left plug into the amp. The two in the middle are the ones that connect to the Metra plugs, and the one on the right is the 12V for the factory unit.

6660956089_2ee6fcb09e_b.jpg



There is plenty of power going into the amp from the head unit, so I don't think it's underpowered. I've tried swapping out the RCAs, but they're all correct. The only way to hear anything is to crank the volume up to like 61, but even on lower volume, the Bass is plentiful.



I'm perplexed.
 

J Everett

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Location
Houma, LA
OK, let me study the wiring diagram again and see if I missed anything. In the meantime, use your stereo's equalizer to turn the bass as far down as possible and the mids and highs up, and turn the loudness setting off if your stereo has one. See if that makes it livable.


EDIT: OK, it's a fairly straight forward diagram, but it shows no subwoofer. The first gen RF system has a sub, right?
 
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J Everett

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Houma, LA
Crap, I just had a thought. You said your head unit only has one set of RCA plugs. What model stereo is it? Some have RCA plugs that are intended to go only to an amp for subwoofers, and thus only carry the low signals.

Also, disregard the above post about plugging it back in and adjusting the settings. You might blow the head unit's internal amp by giving it power with no load on it. Let's figure out what we're dealing with first.
 

NismoFire

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Smyrna, TN
Pioneer DEH-3300UB


Unfortunately, that makes sense...is there a workaround, or do I need to swap head units?


I believe it had a sub in it to begin with, but I don't have one, nor have I seen wiring in the cargo area for one.
 
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J Everett

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Location
Houma, LA
Yup, I just looked it up on Crutchfield. Unfortunately, that receiver only has sub outputs. I know you were looking for an inexpensive head unit, but I think your easiest solution is going to be to return that one and spend a bit more money for one that has full range RCA outputs. This DEH-3400 UB is only $99 and you won't have to rewire anything. It will just plug right in to the harness you've already wired.
 

NismoFire

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Smyrna, TN
Hmm...hope Mom still has the receipt! I picked it out, not knowing it had the amp until I started installing it.
 

NismoFire

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Smyrna, TN
Update: Got the 3400 installed, now I gotta find a resistor or something to go between the head unit and the amp. I can't handle that "POP" every time I change the radio station. The tech at Best Buy called it a "soft turn on" or something, but I'm not sure what the crap he's talking about. He said they don't sell them, but Radio Shack should. Radio Shack, FYI, does not, and I can't find anything similar on Crutchfield.
 

J Everett

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Houma, LA
Those are the numbers of the terminals on the relay. There will be a wiring diagram printed on the relay and the numbers will be visible next to the terminals.

Auto-Relay-12V-40A-4-Terminals.jpg
 

NismoFire

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Smyrna, TN
In the linked write up, which ground do I need to use? It says off the harness, but there is actually two ground wires- one for the amp, one for the HU.
 

J Everett

Suspension Lift
Founding Member
Location
Houma, LA
Nope, not on the harness. Just ground it to the truck itself, wherever you can get a good ground. You can use the harness for your 12 volt ignition sources for 85 and 87 (both should be ignition switched 12v, not constant), but it's way easier to just ground the 86 terminal to the chassis. Disregard the posts after the original, I'm not sure those posters know what they are doing.
 
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NismoFire

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Location
Smyrna, TN
Got it fixed...the relay didn't work for me, so I took it to a buddy and he put 2 ground loop isolators between the RCAs. $20ea at Best Buy and I FINALLY have great sounding audio in my truck.
 
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