why is stereo cutting off

i bought one "75 kingswood holden" australian made old car. tried to install a new stere system. jvc with mp3. installed according to the installation guide. the sounds just cuts off when volume up and back on again. do you guys know what is going on? thanks

there was no amp.

11v-16v is the normal working condition, but i tested it when it cuts the volts is a little below 11v, do you this caused the problem?

i tried to attach the ground to the body, and other locations, the same thing happened.

please help

thanks.

under 11 volts that sounds like your problem. with volume down it plays fine. but up it cuts out makes sence.  is that with the car running? or off? if its when your car is running then you have a charging problem. off sounds like a weak battery.

The batteries proberly been in there for ages, or isnt designed for that vehicle.  Under 11 volts isnt a good thing.  Sounds like at higher levels there isnt enough charge to run the head deck

it happens all the time, with the car runing is a little bit better, but still cuts.

i tested the battery with the car runing about 14.6v without  12v, and i just had my alternator and start motor changed over.

i asked the staff at highpoint jb hi-fi, he said cuting off because the headunit will protect itself from overheating and "common ground" can solve this problem. but it happens even the headunit is cold.

( they charge me $50 to do the common ground for me, but i want to do it myself, is there anyone can link me a diagram , thanks)

thanks

please help again

check the ground wires from the batt to the chassis. and from the motor to the chassis. theres your common ground.