pulling my hair out chasing a gremlin

[Brapster247]

ok let me just start this out  saying that I'm not an idiot, I work as a residential/commercial electrician I've done at least 30 car audio installs over the past 10+ years and besides the occasional little stupid problem here and there I have never been this stumped before. With that being said this is my own vehicle that I'm having problems with

2012 chevy Silverado extended cab totally stock electrical wise besides a optima red top

the setup: Kenwood double din h/u, alpine 500w the cheap one mbp-500 or something like that, jl audio 12tw3 the slim sub under my back seat in a little sealed box with 10 gauge leads 4 ohm dvc in parallel for a 2 ohm load, rockford 1 farad capacitor because I had a bit of headlight dimming, and a rockford 4 gauge wiring kit

now this is where the story starts, this setup has been in my truck for the past 3 years with 0 issues and gets used to its full potential everyday. I mean I've had the volume up for the better part of 8 hour road trips and whatnot it has taken much abuse. so one day I was driving to get a burrito it was about a 20 minute drive and I was bumping slim thug the whole way I was almost there'd I lowered the volume a bit, I smelled something like metal burning and just figured damn the van in front of me must be dragging brake pads or something but after I got my burrito which by the way was great, I got back in my truck to find out I had no bass it was making a a bit of a grinding noise if I turned it up but very faint. I figured ok I burnt something up that was the smell I smelt earlier so I was going to have to do some trouble shooting, this is where it started to get expensive. 

first checked all my wires they were all good so I assume the 500 watt max amp maybe cooked my 400 watt max sub I did have the gain about 3/4, so I took a alpine type s sub I had laying around that I knew worked and hooked it up to get the same very low noise I would call it a grinding or crunching noise. at this point I assumed now ok there is a problem with the amp which was only $100 so I thought ok yea its a pos it did its job lets retire it. went to a local electronic store and bought the alpine s-60 a 600 watt amp that was double the price of the old one great lets go put it in. I get home and install the amp I take that shit type s out and put the jl back in because I think the amp was the problem. everything's buttoned up and I turn it on and I have bass notes again hooray but after I left my house to turn it up (my neighbors still like me) at about half volume the bass cuts out and it goes to a louder cracking and grinding noise for about 10 seconds then the amp goes into protect mode. ok now I'm getting angry I just bought a amp I probably didn't need I go home and I start trouble shooting the wiring, I change the ground to a different spot still does the same thing, I disconnect the capacitor  and run the power right to the amp same thing, I use a rca to aux cord with just my iPod same thing, I try using the rear output on the deck instead of the sub output same, I try a different set of rcas same thing, at this point I'm thinking its got to be a problem with the subwoofer all these different things haven't made a difference the sub is the only thing that stayed the same so I start shopping around. I wasn't spending another $350 for another jl when this one cooked off a cheap amp so I come across an American bass 12 never seen one in person but judging from the reviews the people say its a good sub and it was 800 watt rms 1500 max which Is was got my attention and it was only $160 so I ordered it. now I finally got it and put it in and surprise it does the same damn thing  little bit of bass at lower volumes but when you turn it up you get that god awful noise that makes you cringe. so now I have a new sub and new amp for no reason and still can't get my rearview shaking. at this point I'm getting ready to just take it all out but as I'm sure you know bass is addictive and I've always had it in some form and I can't really do without it.

please don't crucify me and tell me to search the forums and whatnot, believe me ive spent days researching and thinking about what could be wrong I was hoping someone with more experience would be able to help guide me in the right direction because at this point this shits got me pulling my hair out please someone help steer me in the right direction

 

[Mike4068]

Sounds like you need a new hu. 

[Brapster247]

but I've tried it with the rcs from the headunit disconnected and had a pair of rca cable on one end aux plug on the other end with  my ipod hooked up to it and it did the same thing. unless your being sarcastic because thats the only other thing i havent bought yet, then good one. 

[slowfkncar]

Put a dmm on the amp and check voltage during the problem, no other amps right?

[Mike4068]

54 minutes ago, Brapster247 said:

but I've tried it with the rcs from the headunit disconnected and had a pair of rca cable on one end aux plug on the other end with  my ipod hooked up to it and it did the same thing. unless your being sarcastic because thats the only other thing i havent bought yet, then good one. 

No, I had those same sounds a while ago but in my mids and highs. It was the hu. Good luck! 

[SnowDrifter]

3 hours ago, slowfkncar said:

Put a dmm on the amp and check voltage during the problem, no other amps right?

x2

Old wiring - lots of time for connections to degrade, loosen, and corrode. A visual inspection doesn't always tell much.

Even though you moved the ground, it doesn't mean that the wiring, connections themselves are good.

I don't mean to offend with this comment, but most people suck at sealing their connections. 95% of installs are just a ticking time  bomb waiting for corrosion to do the deed. I don't know the details of your termination standards, but you can check by proxy by turning up the volume and checking DC in with a multi meter when measured at the amp terminals.

If you're seeing heavy voltage drop, then start checking stuff. Would it be inappropriate of me to assume you have access to a thermal camera from your employment? Those make connection checking trivial. Get some load on it then look for the hot spots.


Also don't discount wiring inside your box, especially if it has an external terminal of some sort

[Brapster247]

Voltage at the amp is a steady 14.2-14.3 at low and high volume. 

No offense taken snowdrifter ive just seen people get a bit ridiculous as keyboard warriors on forums. As for my ground it is on the body not the frame but i assume it has to be connected somehow if not call me and idiot and ill drill thru the floor and bolt it right to the frame but id rather not. I dont have thermal camera access either, best i have is a infrared thermometer. Clearly you know what your talking about and i appreciate the help

[XSVTOYZ]

voltage is one thing but is the current needed getting there? ok so you pushed the cone and its smooth. you replaced the sub and problem persists. you did slap a dmm and test the speakers resistance?. you said it works fine then starts to break down? is there a certain amount of time? you also stated you routed around the head unit and still it breaks down.  did you check your cables both power and ground? if its a connection issue you should feel heat some where in those paths. I just wonder if you got some corrosion on an old ground. if you  ever did the big 3 it may be time to clean and polish old connections. if you have not done the big3, search the forum.   I was certain of my grounds till in middle of a song I dropped voltage to low levels cleaned and polished till  it was fixed.    

[slowfkncar]

I don't know what else to say, new amp,new sub,steady voltage during load so the connection is good & still did it without the head unit.

when you played your ipod through the amp, did you use the RCA behind the stereo and not connect directly to the amp?  What other aftermarket products do you have in this vehicle?

[SnowDrifter]

14v+ at amp rules out power supply to all degrees. We could chit chat about the benefits of wiring upgrades but as far as OP's issue goes, that's not it.

So now we're looking at upstream and downstream signals

- Verify DC resistance presented by the driver. Turn off your car, leave everything connected, then check resistance at the amp from the output terminals in a quiet/wind free area.
- Visually inspect all speaker wire; inside the box, connections to the sub, terminal cup if used, and wiring to the amp. Resolve any frays/rubbing issues.
- Verify amplifier is cool enough to operate. They can get too hot to comfortably touch but shouldn't ever be like touching a hot skillet. No point anywhere should be above 100c. lower is better, however.
- Verify your remote wire is delivering appropriate voltage when the amp is on and playing at high volume. That receives it's power from the deck, which also draws power and can incur and voltage drop. Internally frayed/broken wires can interfere with the amp's ability to turn on. Issues with power wiring to the deck can, to an extent, be found here.
- Check that your RCAs are plugged in all the way and have good pin tension on both amp and deck side

if you have one available, a 3.5mm to RCA adapter can be useful if you suspect a signal issue to the amp. Hook the amp up to an external device such as your phone and note if the issue still persists