Help. No Bass output from Amp

[Phawstir]

Looking for help with an issue.

My bass amp (Lightning audio LA-3000d) is powering on, but there is no bass output. I hadn't touched anything, but one day i turned my jeep on and heard feedback through my system, turned it off and back on again and my bass output was gone. I've tried a few different things, swapped RCA's, checked power and ground, and pop tested my sub (it worked). My gains and deck are set properly. None of these methods or fixes worked, I am still getting no bass output

I feel like i've narrowed it down to some internal error in my head unit or amplifier that i can't assess. Can anyone give me any insight or recommendations?

[SIDE SHOW]

try plug your phone/ipod straight into the amp via headphone to rca cord, and see if you get any output... headunit might be bugger'd or rca's in the wrong rca output. have you tested your sub with a dmm, also what deck is it?

[Phawstir]

Deck is an Alpine iDA-X303. Just tried playing my iPhone through a headphone to RCA cable, no luck. Safe to say my amp is the problem? any fixes I could try before I send it off for warranty? (would rather fix myself first as I won't be able to send it off for another month when I'm home from school)

[Ahmed Johnson]

If you do anything to try and repair that amp you'll probably void any warranty

[Guest]

find another amp to hook up in its place to narrow the issue down to inputs or the amp itself being the problem

[SIDE SHOW]

^^ this

[firebirdude]

Disconnect the amp from the sub and measure the resistance of the subwoofer at the box's terminal cup. Depending on the failure, a subwoofer can still move from a strong DC voltage being put to it.

If that test's fine, then it's your amp. You've already eliminated the RCA input by connecting your phone directly to the amp. So provided you've got 12V at the amp input, a solid ground and 12V at the turn on.... that amp should be powering up....and given a signal (which you did), it should be outputting something.