i just put a higher powered sony unit in my car, i did have a 4x40 unti and the only difference between that one and this one is this is a 4x50w {jack all} but now at idle it flicks on and off,

it never used to, and there isnt even any sound playing when it goes off, but my headlights are good and bright

do the new systems have a shut off, i.e. below 12V they turn off voluntarily

i had my alternator rebuilt 4 months ago

My suggestion is check over all your connections and check the fuse on the back of the unit also.

yeah id check connections especially earth and make sure its good and the point its earthed to is bare chassis. the other thing is if its on an angle the unit might not like it and is shutting down due to thermal overload, as the convection currents wont flow properly around the unit to keep it cool. i doubt it would shut down as soon as it drops below 12v as if you check the power source and checked it before its probably supplying constant 10-11 volt with it peaking at 12v sometimes. just some thoughts, see if it helps

As the other guys have previously said.... There is something loose at the back somewhere of the unit....

your alternator rebuild sucks

remove power cable from unit, monitor voltage at idle?

alternator output will drop below 12V at idle on your car - but any half-decent amp will have some sort of regulator to filter incoming power.

do the h/l or dash light flicker at idle (in time with the amp tripping)?

check/clean-up fuses and wiring to do with accessory circuit - could be as simple as dirty/stuffed connections ?

does the lite in the cig lighter also flicker? or if that lite is wired to interior lamp circuit, connect multimeter to it to monitor.

Maybe some electronic relay is tripping on and off when the car is idling. You could possibly check the voltage being supplied to the stereo using a voltmeter or something both 1) while the stereo is connected and running ... and 2) when no stereo is connected. Otherwise...check all the power connections and ground connections to make sure everything's connected properly. It's possible that the alternator is having probs as well, since a rebuild doesn't always means it's going to be brand new.

i would check all connections, especially the earth although the unit will switch off below a certain voltage for e.g 9 v, whether the car is idling or not the alternator should still put out a voltage of around 13 -14 volts. A simple way to check if it is working properly is to make your car idle, get a multimeter and set it to the appropriate dc range and measure the voltage of the terminals on the battery while the car is idling, if it is say 13.5 volts your alternator is fine, but if it is say running at 11.5 v, then you know something is wrong with the charging system.

you would have to have the voltage drop to near 9 - 10 volts before the unit would start to drop out.

as has been said above, check the conections. if its at idle (some motors are pretty rough at idle) then it could be causing some vibrations and making it turn on and off... either that or it could be some dry solder joints in the head unit itself...

I had kind of the same problem, my stereo just turn off and then come back on while i was driving. The problem was the battery. I used a multimeter to check and it had the right voltage, but one of the cells had died, so before you go pulling all your stereo equipment apart, and make more trouble for yourself, i would take your car down to your mechanic and get them to do a check.

Then if thats not the problem, then systematically check each part of the car. Until you discover the problem.

Simon

Umm even if the battery has droped a cell, while the car is running, would be above 9 volts (approx voltage when a 12v batt drops a cell, depending on the number of cells in the battery)

Also the car would have problems starting.