4 channel amp turning on/off

I'm at my wits end trying to figure this problem. I don't know it's my amp, battery, or alternator. I have one Kicker sub amp and one Alpine 4 channel amp. The problem lies with the 4 channel amp, it keeps turning on and off. It only happens randomly. I have checked all connections and they are tight. I checked all fuses and they are good. I also have relocated the ground for the 4 channel amp but the problem still continues. The gains are not maxed at all on both amps. I have checked the voltages multiple times and there are the results : All measurements are at car idle. Both amps on : 13.79 volts - 13.81 volts Both amps on and AC running : 13.79 volts Both amps on, AC running, and rear window defroster on : 13.69 volts Both amps on, AC running, rear window defroster on, and wipers running : 13.69 volts Both amps on, AC running, rear window defroster on, wipers running, and headlights on : 12.32 volts There's another wrinkle in my problem. When the 4 channel amp is turning on & off, the voltage at the battery and at the 4 channel amp would fluctuate between 11.50 volts and 12.75 volts. The sub amp is always on regardless of the 4 channel amp problem. When the 4 channel amp finally turn on, stay on, and have sound output, the battery voltage would stay at a constant 14.17 volts. Is this a sign of my battery about to die ? Or signs of an alternator about to die ? Faulty voltage regulator ? 4 channel amp about to die ? I have gone to numerous Auto Zone and O'Reilly's to have my electrical system checked out and all of them said that my charging system is okay. But I would like to have your input. If it's the alternator, is it advisable to get a high output alternator ? And if I do get a high output alternator, do I need to up the fusible link amp rating ? BTW, these two amps are installed on my 300ZX with a factory 80 amp alternator. Any help would be greatly appreciated....Thanks !

is it turning off or is it going into protect mode? does the amp physically turn off or do you just lose sound? have you done the "big 3" upgrade for the main wires under the hood? are your grounds screwed tightly to bare sheet metal with no paint? how many speakers are running off of the alpine amp and have you checked if any are blown? have you checked the connection of the remote wire and made sure it isnt getting pinched anywhere and the connection is solid on both ends?

Thanks for responding so quickly. Sometimes the amp would cut out for 24 hours, sometimes for 15 mins...it's just no telling. It just does it very randomly. The amp is an Alpine MRP-F200. I have this exact setup in the same car for the past 8 years. The only thing I have changed in the last 8 years of this set up is add more sound deadening and change out the head unit. Since I have two amps, I wired in a relay from the head unit remote to turn on both amps (same setup before the head unit change). This morning when I started the car, the 4 channel amp's power led came on and then fades out, then comes on, and then fades out. This afternoon when I stepped out for lunch, the 4 channel amp turned on and have sound through the speakers but after driving the car for 15 mins, the amp would go into the led come on and fade out cycle. I checked the voltage input when it was doing that, the voltage range was 12.95 volts to 13.65 volts. I have done the "big 3". The amp doesn't have a protect mode led, just a blue power led. The ground is screwed very tightly to bare sheet metal with no paint in between. The 4 channel amp is powering two rear filler speakers and front components (total of 6 speakers : 2 rear, 2 front mid-bass, and 2 tweeters). All connections (power, remote, and ground) are not pinched or frayed. Please point me in the right direction because I want to fix the real problem instead of blindly throw money at it. Thanks again !

hmm, sounds like you might have something wrong with the amp. maybe a loose connection or cracked solder joint inside the amp. if it worked fine for 8 years without any changes then thats really all i can see to be the problem. your amp is getting old, i have an MTX amp that ive had in my truck since 2003 and im very surprised that its still ticking, although it does have a loose RCA jack so i have to keep something wedged between them so the audio wont cut out. a car is a harsh environment for any electronics so its very possible that its just on its way out. if you can try to get a loaner amp just to swap with your alpine and see if you get the same kind of problems

Just to echo the above post, I also have an MTX amp that, when not secured evenly would cut the audio as well. I found that out while troubleshooting it, I would put pressure on the amp and sound would come back, release pressure and the sound went away. Torqued down a little more on the mounting screws and all has been fine so far.