Amp not working when car running, working when in ACC

[Al]

Right I've had my sounds in my Corolla for a couple of weeks. All my gear was brand new. Amp is fed with a true 4 gauge power cable from battery to distribution block, then gets fed back as 4 gauge to the sub amp, and 8 gauge to the speaker amp.

I've got one of these amps http://www.sonycaraudio.co.nz/sony-xm-gtr3301d.html driving my JBL 12" DVC sub @ 2 ohms, one of these amps http://www.sony.co.nz/product/xm-gtx6040 running my speakers. I use the throughput RCA ports on the sub amp to the speaker amp.

Up until a day after work this week, the system worked perfectly. Turned the car on, and the sub wasn't going. Drove home, pulled sub out, all connections fine. The amp has power, as the blue light is shining, and the throughput works to the second amp. Now after a little bit of playing around, the sub starts after around 30 seconds when the car isn't running and performs perfectly in the ACC position. As soon as I start the car, it stops and doesn't work until I turn the car off and sit it for 30+ seconds in ACC.

Do I need a new amp or is there something else wrong?

[Al]

Had the Corolla out again today. I was heading home when it was a bit darker and had the lights on, while idling at the lights, the sub kicked back in again, until I moved off, and continued to start and run flawlessly when I was stationary and idling. The idle of the car has always been on the low side, and you can actually notice the headlights increase in brightness when you rev from an idle.

[Dell'Orto]

Check your earth maybe? Might be vibrating around and losing contact

[Al]

Earths are solid as.

[Alex B]

Test resistance of earth & main power feed, test other RCA's, try another acc>amp feed wire.

Bench test amps.

General process of elimination really.

[LEAKER]

Sounds like a speaker wire is earthing out.

[sergei]

When amp is not working when it should what do the power/protect lights are like?

[Al]

Power/protect light stays a greeny yellow all the time.

The same as the speaker amp.

[Al]

It seems to work fine in the morning now? Weird I know. Works till I get to the top of Dyers Pass then it stops working.