HandsFree Car Kit Speaker Hookup

The other reason I usually install the supplied speaker is that when Text messages come through, they usually wont trigger the radio mute and as such, will not go through the car speakers so you wont be alerted when ones come through. Also I don't what car it is going into but I know with the australian Holden Commodore (Pontiac GTO)  the other reason not to feed the signal through the amps is that your head unit must always be switched on for it alert you, as the amps must be switched on unless your amps are triggered differently then using the trig wire on the head unit.

The other thing that I quite often do to these kits is install both extra speaker and audio piping to your car speakers that way you have it through your speakers and can still be alerted when a message comes through or if the head unit is switched off....e.g. you switch the car off whilst still on a  call.