Protection light blinking Alpine MRV-F407

I just put in an Alpine MRV-F407 that was attached to the subs that I put in my car. For two days, they worked without incident. Then, when I started my car, the subs made a rapid bass noise, that's the only way I can describe it. The subs were still playing, albeit not (I don't know the technical term) "bumping" like they had the previous days.
Also, we noticed that the protection light on the amp was blinking red, instead of solid green. My friend, who installed the subs/amp with me, and I got a new fuse and fuse holder to see if that would fix the problem. That didn't work :mad: but I looked online and saw that a blinking red light indicates "RCA ground floated". Not sure what this means.
Any help would be greatly appreciated.
Unplug the RCA cables from this amp. Power it back up. If the red protection LED is still flashing, the problem is in the amp. If so, it may be as simple as repairing a solder joint from the RCA shield to the circuit board.

If the LED does not continue to blink and remains solid green, use an ohm meter and measure the resistance between the outer contact of the RCA plug and the radio chassis. This should read about zero Ohms. If not, that is your problem the radio's RCA shield needs repaired.
Hi. Old thread but Same issue. I used this amp many years ago without problems. I got it from the garage today and wired it in. Two green lights but the protection light is flashing red The bass (I’m using it as a single channel for a sub) is coming through but in reduced quality and the Sound is awful due to the fault. The amp light acts the same way if RCA are plugged in or left Unplugged. Is this really an issue with the rCA or could it be something else. I’ve opened the amp up and inside looks brand new like it’s just left the factory even though it’s probably 20 years old at least. Thank you for any help
I am hoping the original poster with the same issue can tell me what he did to fix it. I searched the forums to find a thread on the subject so that I wasn’t taking up more space starting fresh thread as I thought that was a good thing to do. But if it’s an issue I can make my own. It just Seems silly though when it’s already here with the people who know about the issue here too.