This problem is driving me insane as I can't figure it out.

Whenever I turn up the bass, it starts cutting out. If I have it somewhat loud, once it hits a certain point, it will stop working, then work again (repeatedly) It's like I'm taking the volume control for the bass and keep tuning it up, down, up, down.
If I look at the capactor while it's doing this, it shows the voltage drop down to > 8 volts at times when the bass is hiting hard (while the car is running too). Sometimes I'll have it perfect where there's significant bass, then all the sudden it cuts down, and I have to turn down the bass enough until it starts working again.

I recently got this amp last week and haven't been able to get it to work right yet. My speakers are wired for 1 ohm, and I verified it with an ohm meter.

Another thing is, I've got to have the gain on the amp, as well as the remote maxed out just to get some decent bass outta it. It was never like that with my old Kenwood 600.

One theory is a bad ground. I have the ground wires going to the rear passenger seat belt anchor. I scraped all paint off the metal and I used that as a ground for the past 3 years w/ no problem using my Kenwood.

I've tried bypassing the cap just in case that was causing it, no luck.
I'm using 4 gauge wire, BTW.

Specs:
Diamond 600.1 mono amp.
Two JL Audio 12" W3s, dual 4 ohm voice coils, wired in Parallel for 1 ohm.
When I first hooked up the system with the new amp, I had the woofer wired for 4 ohms and it was still cutting out, only the bass was so weak, I could barely hear it with everything maxed out.

 

Is that amp 1ohm stable in mono? Try rewiring the subs to the amp in series. It will take it from 1ohm to a 4ohm load on the amp. Leaving the subs wired as they are, but where they are wired from to the amp.

 

Yes, I specifically got this amp because it can handle 1 ohm.

The specs are here