Sub or amp dying...thoughts?

[Broncoholic]

Posted in Audio, but checking here for input too!

Sub or amp dying?

I'm trying to determine the most likely failing component. - sub, amp, or maybe signal from head unit? 2003 Expy Eddie Bauer with full factory system, 6-disc in dash changer. I've had this truck 20 years and never had an issue with the audio until recently. A couple months back, the subwoofer...

www.expeditionforum.com

I'm looking for any suggestions to chase. Thanks in advance!

 

[whtbronco]

If you have no sound at all it's not likely the sub. If the sub blows you'll get crappy sound, but sound none the less. If it failed all at one I'd be looking for a fuse, I can't recall off hand if the sub can be turned off in the radio settings. Oh wait it can be sort of turned off, if the fader is set all the way to the front it will turn off the speakers in the rear door and and the sub.

 

[Broncoholic]

It's def not a fuse because in the last 36 hours, sometimes it works, sometimes it doesn't, sometimes it works half. I'll play with the fade to see what may change. Thanks!

 

[whtbronco]

From the other conversation here's the pics.

 

[Broncoholic]

Right on, thanks!

I ran to the home improvement store tonight and the sub seems to work better when I'm slowing or stopped, like inverted speed sensitive sound adjustment (the wife's 2016 increases sound with speed to compensate for road noise). Makes me think loose connection where the weight of wire harness is just enough to make a difference in connection. No bump or popping noise today like yesterday. Adjusting fade front or back didn't make a noticeable difference; neither does using the adjustment for driver seat / all seats / rear seats.

I really hate electrical gremlins.

 

[whtbronco]

Ugh, I agree on them dang gremlins. This is why I want my next truck to be another 78 Bronco. There is so little electrical crap and what's there is dedicated wires and simple to understand.

Is it working better or is it just that you have so much more noise to drown out while rolling down the road the sub simply can't keep up? Either way my thought is that the head unit is okay since it's sending the signal. It could be a wire, but I'm thinking it's either a connection with the subwoofer or the amp is failing.

 

[Broncoholic]

Thanks for the sanity checks. I'm hoping to investigate Wed or Thur. If not, then it'll be a couple weeks before I get time again.

 

[Broncoholic]

Thursday my truck wouldn't start. I pulled the battery (16 months into a 36 month warranty, so free replacement) and pulled the alternator (lifetime warranty through AZ). I was thinking maybe a dying battery or dying alternator may be causing an audio issue at the amp. I was told the battery had a bad cell - free replacement. AZ didn't question the alternator - free replacement. Electrical system worked great Friday, but the sub was acting the same, so electrical issue not causing sub issue. Parked the truck, went out of town and came back 2 days later. The new battery wouldn't start the truck and the amp is 30 degrees F hotter than anything else inside my truck (150 degrees F vs 120 degrees F). When I unplugged the amp connector, the sub "thumped" even though I hadn't cycled the key in the ignition. All I did was unlock the truck, open a door and access the amp. I'm certain something in the amp has shorted and it's trash. It appears the audio/amp issue probably caused the electrical issue!

More troubleshooting to follow!

 

[whtbronco]

Yeah it sounds like the amp was on for sure.

 

[whtbronco]

Sub assembly.

 

[Broncoholic]

So the new battery was toast and I got it replaced under warranty. I got the factory amp and replacement sub from @whtbronco - MUCH appreciated! I swapped the amp out and it drove my factory sub pretty good, so my amp was definitely shot/shorted out inside. With that confirmed, I had to disassembly the entire side to swap the sub because my factory equipment was dual voice coil at 2 ohms, but @whtbronco's is single line at 4 ohms. A couple hours later and everything is back to good... actually a little better I think with that MTX!

 

[whtbronco]

Great news, glad to hear it's working for you. Glad to help.

 

[whtbronco]

Did you close up the bolt hole in the back of your enclosure? That seemed to make a difference in mine, though honestly maybe it was just my imagination.

 

[Broncoholic]

Did you close up the bolt hole in the back of your enclosure? That seemed to make a difference in mine, though honestly maybe it was just my imagination.

No, but I thought about it. The magnet was snug against the back of the enclosure where the hole is. I added a weatherstrip foam around the mating surface of the sub and added a piece on the magnet at the hole. It seems to be sealed quite well. Like I said, I think it hits a little harder than what I had. Could be placebo, but I'm happy with it! The factory system is nothing without that sub.

 

[whtbronco]

Yeah sounds like you got it sealed well. The MTX was certainly better than our factory sub, but as you noted it's not identical to what you had.

Yep, definitely needs a sub to sound right. Better speakers and more power help that, but I wonder if part of the need is due to the size of the Expedition.