HU in conjunction with OEM sub amp

I am trying to figure out if I can use my aftermarket HU to power the factory amp on my 03 Eddie Bauer Explorer. I really want to avoid the expense of an addition amp right now, I’ve already got one powering the four front channels, and just want to fill in the bass for now. It doesn’t need to be too powerful

I'm pretty sure the factory amplifiers use a high-level signal input, and all you need to do to integrate an aftermarket head unit into the system (and keep using the factory amps) is the standard ford harness.  Depending on the power output of your head unit, you might need a converter like the PAC OEM-2 to dial down the output a little bit to make it more compatible with the factory amps, but you should try it first and then see if you need the converter.

There is no way to power the factory sub with the aftermarket head unit's built-in amplifier.  Really using the harness is the only correct way to integrate with the factory amps.  If this vehicle just had the standard stereo system then it would be a direct connection to the speakers, but still it would use the same wiring harness.

Unfortunately, the subwoofer amp is using a different connector than the one addressed with the standard Ford Harness.  There are three connectors on the back to the OEM stereo:

1 - standard connections (power, ground, front/rear speakers

2 - output to sub amp

3 - steering wheel control interface connector

I was hoping to take the front speaker output from the standard Ford Harness and splice it into the wiring going to the sub amp, but I don't know if this will work.

Ahh yes the infamous ford square black plug. Okie I think I was wrong about the high-level output thing.  I assume those readings of "4.88" and "6" on the oem head unit's output wires were in volts?  Assuming that's the case, then your sub amp has low-level inputs.

If you are going to try and hook up the sub to the aftermarket head unit's extra set of output channels, you have to run speaker wire all the way back to where the sub is located, and bypass the factory sub amp (probably located on or near the sub).  You might wanna test the resistance of the sub first to make sure you won't fry your head unit.

Like I said before I wouldn't really recommend trying to push the sub with the aftermarket head unit's amp, but it is theoretically possible.

you can continue to use the sub amp and sub, you just have to figure out how to send a low-level signal to the appropriate wires.  A short RCA with the end plugs cut off one end would do the trick.  The plugs remaining go into the aftermarket head unit's low-level outputs for the rear channels, and then for the bare wire ends, the center conductor of the RCA is the positive wire, and the shield is the negative.  In this case both shields use the same connection to the factory wiring.

What's the preampt output voltage of your aftermarket head unit?  You're going to want to get it as close to 4.88 volts as possible.

The HU is Pioneer DEH-P7500MP, which is supposed to have 4 volt pre-outs.  I have the Front and Rear pre-outs going to an Alpine amp to drive the front and rear channels.  I would prefer to use the Sub pre-out to drive the factory sub amp and sub.

What I understand so far from your message is that you believe this can be done by cutting an RCA cable, with the plug end going into the sub pre-out and then splicing the cut end into the factory wiring going to the sub amp.  The inner wire is the positive and the outer shield is the negative.  I don't understand what you mean by "both shields use the same connection...".

Which pin wires should I connect each RCA cable end to?  The two negatives to the wire at pin #1 and the two positives to pin #2?  What would I connect to the wires at pins #3 and #4?

Yes, the readings were in volts.

Well, I got it done and it sounds great!  Really helped to fill out the sound.

I spliced an RCA cable into the wiring harness using the neg (shield of the RCA) from the left HU output and the pos (inner RCA wire) from the right HU output.  Then spliced right into the ACC power line to power the amp.  Turned it on and I've got nice bass!

I didn't have to use a loc because I've got 4v pre-outs that I was able to use.  The HU allows me to select the crossover frequencies for the sub and also add or remove bass boost.

The only problem that I have noticed so far is that the amp doesn't have a soft power on, so I end up with a slight pop from the sub on power up.  Is there any sort of line conditioner or anything like that that can be used for amps with a problem like this?

Awesome! Glad to hear that worked out so well.  And you can even control the volume of it and everything!  good deal.

Actually I just answered a question very similar to this just the other day.  It's even easier for you since you already are using the car's +12 volt switched wire to turn on the factory sub amp.  What you need to do is get a N-66A turn-on pop eliminator, and this will go inline on the head unit's red +12 volt switched wire.  Just make sure you put that N-66A AFTER the connection to the amp turn on that you already made.

When you turn your car on, the amp will power on right away because it's getting it's turn-on straight from the car's switched wire.  Normally the head unit would turn on at the same time, but what the N-66A does is prevent voltage from passing through it (and out to the head unit's switched power wire) until 2 seconds has elapsed.  By that time the factory amp will be fully powered up, and you should get no turn-on thumps.

The N-66A is actually adjustable, from 0-30 seconds supposedly, so you can fiddle with it  if you don't want to wait 2 seconds.