How to re-start the cars own amplifier
Many late model cars will have their own
amplifier or antenna amplifier which will more often than not be powered from the original head unit.
With any aftermarket unit these will need to be re-powered. The
methodology is quite simple.
With the old stereo unit connected probe and isolate each wire which is powered when the unit is
on. Then disconnect the plug from the back of the unit and re-test these
wires. The wires which no longer have power going to them when disconnected from
the head unit need to be re-powered. These power wires could be running
power to the amplifier or the antenna amplifier and need to have 12V
re-connected to them.
2) For the external amp: if you can locate the amp, then using the original unit connected probe
each input and isolate the power wire. When
installing a new unit then again make sure this wire is powered