Mach Stereo Intermittent Subwoofer issue

[Sedare]

This is one of the few issues that I have had since I bought this 3 years ago. I was digging thru the forums here, and I found one post about this issue in 2014, but no one followed up on it.

The stereo is decent, 6 disc changer in the armrest hasnt ever worked, but I dont care about that to be honest. The issue I have been observing for these 3 years is how the Subwoofer will turn on and off with no comfirmed cause.

The Subwoofer works under a few conditions, but not a guarantee to work.

Temperature is 25-40F outside. It will stay on for a while, often until I turn the car off, in fact I had it working for 4 hours on a drive to Seattle last year, but not after I parked the car. In the last 3 months when it does turn on it has occasionally turned right back off after 30 seconds, or one time it shut off 5 minutes later. Some parts of the year when it is warm, it will not work for months on end. I have checked the wiring, and I have found no damage, and signal from the deck is stable to the amp, and the wires have no shorts.

When it turned on a while back, I was parked in a parking lot, and I opened the tailgate, and just started hitting the side of the interior panel trying to get it to shut off. Nothing happened. I beat the car everywhere the wire travelled trying to find out where the assumed wireshort was. Nothing at all. I got so pissed off I started kicking the shroud around the stereo, and still nothing changed, the sub stayed on. No I did not break other crap. But it confirmed my wire testing. Everything is fine.

But then it stays off during cold days when it was otherwise working fine the few days before.

So last fall I started to notice an icon on the stereo that shows up when the subwoofer is on.

It is a small headphone icon. When that is on, the subwoofer is working.

http://www.shareamemory.com/radio/2003_09_06.JPG Shows the icon I refer to.

When this icon is not present, the sound quality in general is worse, and the subwoofer is off.

When the sub is off, I have noticed a lower quality sound issue when listening to the radio. It will fade from a better quality to a lower quality as if its based on the antenna reception. Or maybe I have an output issue from my alternator? I replaced it last year tho, and the voltage is correct. I just have tons of discernment on this, but nothing that has helped me fix this yet.

At this point I am left to conclude that the Deck itself that is malfunctioning, or some sort of non connection based error. Firmware? Is there a bad relay inside the unit? Is this even repairable?

 

[J_C]

I'd wonder if the sub amp circuit board has broken solder joint(s), pull it out and examine it.

Other than that, I'd wait till it wasn't working then check both ends of every wire for resistance, and inspect the plug contacts for corrosion. Similarly with a multimeter you can try to probe for any audio signal or communication between the console head unit and the sub.

Seems like it has to either be a communication issue (which could still be a broken solder joint on the amp board) or the head unit itself, since you're seeing the sub icon on the display go on and off.

 

[Sedare]

I'd wonder if the sub amp circuit board has broken solder joint(s), pull it out and examine it.

Other than that, I'd wait till it wasn't working then check both ends of every wire for resistance, and inspect the plug contacts for corrosion. Similarly with a multimeter you can try to probe for any audio signal or communication between the console head unit and the sub.

Seems like it has to either be a communication issue (which could still be a broken solder joint on the amp board) or the head unit itself, since you're seeing the sub icon on the display go on and off.

The solder issue fits due to the temperature range part. I guess I always thought the warmer components get, the more likely they are to make contact, not the other way around.

I will see what I can figure out. This is a backburner project, I will randomly bump this when I manage to test this stuff. This is mostly just a rainy day post.

 

[gmbroy]

when the headphone icon is on your stereo is receiving the fm signal in stereo & thus the sub woofer works, when it recieves a weaker fm signal it recieves it as mono , the icon is not on & the sub does not work .

 

[Sedare]

when the headphone icon is on your stereo is receiving the fm signal in stereo & thus the sub woofer works, when it recieves a weaker fm signal it recieves it as mono , the icon is not on & the sub does not work .

This would have resulted in the CD player, or even tape adaptor(with my phone streaming music) allowing the subwoofer to be functional all the time.

This was not the case.

 

[gmbroy]

you said the cd player did not work & never said anything about the cassette player or streaming music .

 

[Sedare]

you said the cd player did not work & never said anything about the cassette player or streaming music .

I said the 6 disc didn't work.

I also just realized I never even said what car I am working with... But knowing it's the mach stereo, and that I have a sub, I assumed the cd and tape I the deck was common knowledge. Sorry.

 

[J_C]

So it seems possible that the stereo (headphone) icon and it's disappearance, along with worse sound quality, is just coincidence. For the worse FM reception I would try unplugging and replugging the stereo rear antenna cable a few times, and at the junction of the cable to the fender antenna.

At that junction mine even had water buildup in it, apparently rain runs down and pools inside so after I cleaned the junction out and plugged it back in, I smeared some dielectric grease around the connection seam. Sounds easy but the !@#$ wheel well liner has to come out to get at that connector IIRC. Guess it was still easy but more work than it could have been.

 

[CDW6212R]

Interesting, I hadn't read of that before.

FYI, the console wiring is part of the circuits required for the sub to work, and don't forget also that the rear controls might have some effect, even if it's a logic issue. I have the console out of two of my Mach SUV's, and I noticed the first time that the sub didn't work any longer.

It also cut the rear speakers I think, I forgot since that was 2006 when I rewired my 99(no sub but aftermarket deck, had to jump the speaker wires in the dash console connector IIRC).

I would check the wiring to the console if you can, plus play with the rear controls, see if anything changes. swapping the sub amp might not be bad, if you had one handy. I've got a spare someplace.

 

[Sedare]

If I have to invest into the stereo, im just going to leave it as it is. The next chunk of cash I put into this thing is probably going to overhaul the engine that is leaking oil, or fix the transfer case/front diff whine noise. 306k miles will do that to the V8.

Seeing how seemingly non wire short this issue was, I half expected it to be a common issue. Im not worried, I love this car. If I do manage to figure out the exact cause I will update this.