Line Out Converter Feedback/won't turn amp off

[neonhomer]

I have a friend of mine who just bought a new Chevy truck, and wanted to get his bass back. Skipping over the non-important stuff, he installed one of those line out converters (the Axxess AX-MLOC720). The amp is a Tezla 1500.1D. Sub is a Sundown SA-15 w/ SPL cone. Truck is a 2015 Chevy Silverado 1500 Rally Edition.

When he shuts the truck off and gets out, the amp doesn't shut off. After about 30 seconds or so, the sub will start "going off" (I'm assuming it's some sort of feedback the amp or LOC is picking up).

The LOC is wired to the Driver's rear speaker for the signal input.

After it did this a couple of times, he pulled the amp remote wire (provided by the LOC), and the amp shut off, but the LOC remained on.

Then it decides to start working right. Shuts off when the head unit (factory) shuts off... Then it started acting up again, but this time he wasn't near the truck to catch it to stop it. Came back out to his truck to find the cab full of smoke and the sub cooked.

There are three questions here:

1> What is happening?

2> How to prevent it?

3> How to tap off the factory radio for a signal to fee the amp.

[MADVIBES]

The easiest way is to run a wire to a fuse in the fuse box that is switched power. That way when he turns the truck off the amp dies regardless.

[neonhomer]

That was my comment to him when he first had the problem. Run a manual switch, or find a keyed hot to turn the amp on and off.

This is the same guy who "knew what he was doing" and fried a Soundstream 15 because he had the gain all the way up and bad power.

The upside? I might end up with a Sundown SA-15 that just needs a recone!