Having a problem with a long-time set-up, there's been no changes to the system.
I get 12V at the power terminal when the car is off, the remote wire gets 0V. So far so good.
When I turn on the radio, I get 10.5V at the remote terminal, but only 4.5V (?) at the power terminal, amp does not come on.
Then I applied external 12V to the power terminal, the amp switched on and played normally. All I had to do was briefly touch the external 12V to the terminal and it would stay on. If I switched off the ignition and turned it back on, the amp didn't turn back on. I did this about a half-dozen times.
The last few times I tried it, the amp would turn on when I applied external power, but wouldn't stay on when removed, the sound would quickly fade out and the amp would turn off. If I maintain external 12V, it works properly.
Since power seems to be working as it should, I'm guessing my 20+ year-old amp has given up the ghost (I'd guess a relay or capacitor), but I thought I'd see if there was something I was missing.
I have the same problem where my amp has just suddenly turned off, and now theres no power init, or the subs. All the speakers have gone bakc to default car speakers. I used a tester Screw driver on all the cables along sub and amp and battery connector, stangely enough no lights come on, even fro mthe car battery? Do I need ot use a multimeter to check these cables? Anyway thats not my biggest worry. My sub was working absolutely fine, when one night I noticed after a while that theres no more bass.
I've checked the 40A fuses in the amp and they seem to be in tact. I've also checked the big gold fuse in the see thru container which also seems fine (no signs of corrosion or melted, or broken or chipped etc). I wanted to diagnose the problem myself before resorting to an engineer.
You could try wiring the remote wire to a relay as a trigger. And have a stronger power source from your battery power up the amp. Either that or try changing your remote wire to a larger gauge.