99 Expedition EB Mach audio system problem

[Djarratt2607]

99 Eddie Bauer with Mach audio system. when I got the truck the radio didn't work. I originally assumed it was the head unit and replaced it with one from the junkyard that had the STOCK audio system, not the Mach. The head unit wound up not being the issue, it was a fuse. The radio and disc changer work now, and all 4 speakers have power. However, the rear two speaks are very quiet and there is no Bass whatsoever. The amp, sub and all fuses seem fine. My question is, could it be because I replaced the HU with one from a vehicle that didn't have the Mach audio system? Maybe the one I put in doesn't have the pins for the sub/amp? Are the HU's different for the 2 different systems (stock/Mach)? Any guidance is appreciated.


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[Aspen03]

Likely both. The Mach has an amp for the sub back on the rear of the vehicle and the the speakers are driven via an amp below the radio, it's a little to the left as well, not directly below.

You're probably missing output for the sub and feeding the wrong type of input signal into the factory amp for the rest of it. I would source the correct HU or find a different amp to run it all. If you're planning any sort of speaker upgrades, go with the latter so you have proper power for whatever you choose.

 

[Aspitler24]

I have the exact same issue, except I have the original head unit and haven’t done any audio or electrical repairs lately. I got in and started it one day and it sounds like the front speakers work but the very back do not, with absolutely zero bass. No matter the setting or type of music, it sounds like a really really old radio program.

 

[NDNplanner]

To solve my audio issues I did a fresh install in my '97 Expy with a modern touch screen radio, ran fresh wires to my indoor speakers and replaced the amp in the passenger side rear panel. If you have the time, particularly in the era of Covid-19, you can have a bumping system on the cheap if you have the time.

 

[tekrsq]

I've got an aftermarket touchscreen Pioneer in my 99 EB (with the Mach system). I'm no electronics specialist either. I just hooked up the new system's pigtail to the stock harness and everything works as it should. I can even turn the sub woofer on/off at the head unit.