head unit power on off switch

On modern or head units manufactured within the last 15 years. Head units that use: Red wire for car Accessory switch. Yellow wire to maintain clock time & radio station presets. When you turn off the head unit with the head unit's on and off switch. Is the head unit still drawing voltage from the battery, other than the voltage drawn from the yellow wire to maintain clock time & radio station presets? Another words is the Head unit complete off when turning it off by it's on & off switch? Is the red wire used as a trigger for an internal relay? What wire is used for head unit system power red or yellow?

Acoustical Levitation

Off = Off, whether it be powered off via deck's switch or ignition switch.  The red wire is simply a voltage sense wire.  All power is provided through the Yellow wire. 

i am an idiot wrote: Off = Off, whether it be powered off via deck's switch or ignition switch.  The red wire is simply a voltage sense wire.  All power is provided through the Yellow wire.

So if you do not disconnect the 12 volt battery power to the RED wire but turn off the Head unit with Head unit's on and off switch the Head units front panel light turns off but the internal electronics are still powered up. correct? Sounds like the RED voltage sense wire works kind of like the old Fosgate power amps. Head unit RED wired is wired into power amp. When Head unit was turned on, the amp would sense power draw thus turning on amp and sending 12 volts to the head unit through the same wire. check out below

Acoustical Levitation

hi, the old Fosgate circuitry would be current not voltage sense. remember back when those amplifiers were made not many radios had a remote out lead, or even a memory lead. the radios had analog tuners and mechanical tape transports. mark

Ween wrote: hi, the old Fosgate circuitry would be current not voltage sense. remember back when those amplifiers were made not many radios had a remote out lead, or even a memory lead. the radios had analog tuners and mechanical tape transports. mark

Hello, On 2012 head units is there a battery draw if you don't take 12 volts off the RED wire? (other than the draw to maintain radio station presets and clock time.) Thanks

Acoustical Levitation

Back in the day of the Rockford and Pioneer current sense circuits, the red wire powered the radio.  If the radio had a Memory wire, that is what it was, memory to power the clock and memory for presets.