I am trying to add an amp to the factory system on my 99 Explorer Limited. I am rather frustrated at this point. I have the amp wired up properly (power, remote turn-on, ground) but CANNOT get the speaker wiring right. Originally I plugged into the left rear door speaker and used the high level inputs on the amp. Didn't work. Next, I bought a high level to rca converter and that isn't working. From what I understand, the factory amp is part of the head unit. Is this my problem, the amps cancelling each other out? I tried to find the speaker wires going into the rear factory amp and sub (I know this is on the passenger side by the rear wheelwell) but I can't seem to get the torx bolt off for the seatbelt so I can't get the panel off. I do know where the wires are under the seat (the ones that lead to the factory amp/sub in the rear) but I don't know which are the speaker wires. I also know I can get an amp bypass harness but will it work if I am keeping the stock head unit?

HELP! Basically, what's the best way for me to add an amp and sub to the factory system?

 

u will need to bypass the factory amp in order to add a amp and sub. im almost positive on this. i actually forget where i read about this, sorry i cant help more if i find it ill post it.

 

If your explorer came with one of those "premium" (whaddajoke) systems, it is very likely that you won't be able to simply step down the line level input (the output from the factory amp is just too high to begin with)...

And even if you could, it would hardly be a sound quality improvement...
You'd have the signal coming from the head unit, going through the first amplifier, through all it's circuitry, getting amplified by what amounts to a cheap amp (I'd have my suspicions about it's linearity and response), getting stepped down again, going through another amplifier and all it's circuitry...

The chances of getting a clean signal (sound) out of the second amp would be greatly reduced...
And in the event that you didn't get a clean sound... how would you go about determining why it didn't sound good.. which is the culprit?

To properly add an aftermarket amp in this scenario requires one of two approaches:

1) Replace the factory head unit in addition to adding the amp. In doing this, you can run an RCA cable to your aftermarket amp, unobstructed. Be careful however, not to use the factory wiring to the speakers (it's common to run your speaker leads from the amp to the dash, and make your connections to the door speakers there), unless you have confirmed 100% that the "premium" system amp is inside your head unit, and not remotely mounted elsewhere... or you could recreate the same problem all over again!

2) Use an adapter meant for this scenario. I have installed two PAC OEM-1 devices in the past couple years, and they seem to work very well, they are avaialble here, or anywhere that sells PAC:
http://www.tune-town.com/Cars/stuff/pac_oem1.htm
What this device is, is a 'black box' that allows you to either retain the factory head unit and add aftermarket amplifiers... Or allows you to add an aftermarket head unit while retaining your "premium" stereo, depending on which cables you buy for it.
In addition to this little 'black box' you need to buy two of three types of cables made for it, some of them specific to your particular car:
A-type cable: Used to interface aftermarket stereo to 'black box', to add a head unit to a factory "premium" system
B-type cable: Used to interface 'black box' with your car's factory wire harness that plugs into your stock head unit, when replacing the head unit. (AMP-RCA cable is used when adding and/or bypassing aftermarket amplifiers, however.
C-type cable: Used to interface 'black box' with your car's factory wire harness that plugs into your stock head unit when adding and/or bypassing aftermarket amplifiers.

Using this little device is a very easy thing...
Plug your AMP-RCA cable and appropriate C-cable into the OEM-1 'black box'..
Unplug the factory harness from the head unit..
Plug it into the female plug on the C-cable..
Plug the male plug of the C-cable back into your head unit (restoring that connection)...
Plug in your RCA's, use the potentiometers to make your gain adjustments, and you are in business!

 

You will have much better luck if you locate the wires by pulling out the factory radio. In fact, you can go to a local retailer and look at thw wire harness adapters they well. That should show you which wires on the factory harness go where. Then splice into those wires at the head unit before they go through any amplification. Then you can take thoe leads to the amp as high-level inputs, or convert them behind the radio to 100 ohm RCA output, and run that cable into the low-level inputs on the amp.

I suggest the 2nd approach.

Andrew
www.subbox.net