Mach 460-tweeters not working when engine on


New Member
Oct 18, 2020
So I had an 01 gt and installed an aftermarket HU. It simple and worked great. Long story short. I now own a 99 cobra and it already had one in it. I was planning on putting mine in anyway because it is much better, but soon after I bought it, I hit a bump and then the tweeters stopped working.

Now, when I clutch in and brake they work, and as soon as I take my foot off they die. When I have just key on or accessory they work fine. Even more complicated, I now get a pop when the amps get powered. I had a step down in my old HU in my gt to prevent this, but this didn't happen in the cobra until that bump.

So I try and install the HU from the gt and wire it up. I have the step down in from 12v to 5v to supposedly eliminate that pop, but I have the same issues with this one. Pop on startup and no tweeters when engine is running.

My last thought was maybe the wiring harness we are using is not correct. Maybe I made a mistake and the previous did on his. He kept the OE radio and gave it to me, so I install it back in and the issues are still there.

I have basically ruled out the aftermarket HU and radio side harness. My ideas are bad ground? Loose connection? I really think I just have a bad amp. Anyone else ever have this issue?
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