Need some help with subwoofer thumping

[Masonk]

So I have a huge box for my 2 12 inch kickers on my backseat of my truck and occasionally I just unplug them to make extra room for passengers. It has always worked fine, but last time I put them back in and then they started thumping, not a hum or anything. I messed with the gain on the amp and redid the ground. I even tried running new rcas away from any other wires and it still happened. It happens whenever I'm on the aux mode of my head unit. If I put it on standby or turn off the head unit the noise goes away. Both of the subs do it too btw, and they're wired correctly after double checking

I'm totally lost on what could be happening, but it seems like it's the head unit based on my findings. I'm just not sure what would have changed on the head unit from taking subs out.... any help is appreciated. Thanks a ton.

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[BrockSamson]

This amp has 14 gauge wire, another site i was looking at suggested 15 amp fuse (based on wire size).

 

[Masonk]

What do you mean?

 

[Boomin_tahoe 5,000+ posts]

Could be a number of things: Bad ground, although you did say you re grounded the amp, the power wire is loose from the amp/battery. RCA's could be bad or even the HU might be bad. Try a diff HU and see if the problem still there.