2 systems, sub feeding back

So recently i set up my buddy with a LOC in his monte carlo, pulling signal of the rear speakers to the LOC and of course running amp +/- like normal, He bought the metra/ axxess LOC you can get a best "crap" buy but i have used axxess LOC before with no issues so i wasnt concerned. THe LOC has a bunch of wires 4 for the line level and then a ground, power, remote and ref ground, instructions states -/+ and remote can be connected to the amps terminals so i did that and if noise is present you can use the reference ground. Well when running everything is fine but one the car is off shortly after the sub feedback alot and only stop when the L rca is removed from the LOC or other random ways like unlocking the car or opening a door? Any ideas? The second system this happened to me is my gf's mountineer which i have had an older axxess ALOC60 or whatever installed in for over 2 years with no issues. I put an aftermarket HU in but still left the sub running of a LOC because i just havent gotten around to running rca's back to the amp. I never connected the HU's remote wire because i didnt need it but decided since i remember the cars wire harness had a wire for remote turn on id connect it to make sure the cars internal amp was on, i left that remote connected and suddenly when visiting family her subs began to feedback so when back i disconnected that 1 remote wire and still when the car is running but the HU is off the subs feedback? Her LOC only has 4 wires for line level/ RCA out and 2 brn wires im not using and never hooked up? Why after 2+ years are they feeding back? ALso when i remove the rca cables from LOC >amp no feedback. Sorry for all that please help???

Feedback?  What do you mean by that?  From your description is seems you may have cross-connected signal ground and power, or you may simply have the gain way too high.  In the second case the simple answer is something broke or a connection got damaged or changed.  Disassemble and troubleshoot.Support the12volt.com

Thanks ill check gain in the first system and troubleshoot the second and report back. Explain crossed signal ground and power

If the LOC ishooked to the rear speakers, and the sub is in the rear. AND the amp is signal sensing to turn on. That is your problem.  Any movement of the rear speakers is sensed as input to the amp, this will turn on the amp, and start a feedback loop!

ac0j wrote: If the LOC ishooked to the rear speakers, and the sub is in the rear. AND the amp is signal sensing to turn on. That is your problem.  Any movement of the rear speakers is sensed as input to the amp, this will turn on the amp, and start a feedback loop!

Turns out it was the amp gain just tested today. Problem solved. Now i just need to test system #2. Thanks

Does her amp have a phase switch? If so switch it to the other setting.  If it does not have a phase switch, what are the chances she removed the box and possibly wire the speakers out of phase from their original configuration?   At the amp or at the speaker enclosure, reverse the plus and minus speaker wiring of both speakers. 

Run the RCA cable and your problem will go away.  For future reference, install the LOC behind the radio, this way you will not have this problem with the oscillation.  And you would already have the RCA cable at the proper place.  LOC connected at the rear speaker will cause problems.  Connected to the same wires, just at the rear of the radio will work fine.