The keying wire itself draws little current, it just provides a signal
voltage to the unit to put it to sleep or wake it up. The designers
assume that you don't want to draw a bunch of amperes through your
ignition circuit, so it's the the always-on wire that is the main source
of power for the unit.

How much current the unit itself draws from its always-on wire when
asleep (standby) is a matter of design. But the key wire is not a
significant current-drawer.

What I'm saying is that you can put the unit into standby with the key
wire and it can still be drawing hundreds of milliamperes through its
always-on wire. That's the one you have to watch out for.

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.

On 09/01/2015 07:30 AM, Jim Felder wrote:
> I remember when you went through all that, about the same time I bought
> my radio. So, using the keyed hot wire will draw very little or no
> current? I like the idea from a previous post that I could install a
> switch to connect it to either circuit, aways hot and switched hot.
>
> Jim
>
> On Tue, Sep 1, 2015 at 9:26 AM Rocket J Squirrel
> <camping.elliott@gmail.com <mailto:camping.elliott@gmail.com>> wrote:
>
>     Many car stereos/radios don't really turn off. They mute and the front
>     panel goes dark, the power amp sections shut down, and the controls go
>     to sleep, but they are still partially on and drawing current. I guess
>     the manufacturers assume that you drive your car frequently.
>
>     The current draw is through the main power wire, the other wire,
>     frequently connected to the ignition switch, doesn't draw much current
>     at all -- it is used to signal the unit to wake up.
>
>     I had to search high and low to find a unit that actually powers off --
>     not only from the front panel power button, but from the remote, too. So
>     I could turn off the music when I get into bed rather than have to lean
>     up to the dash to shut things down.
>
>     --
>     Jack "Rocket j Squirrel" Elliott
>     1984 Westfalia, auto trans,
>     Bend, Ore.
>
>     On 09/01/2015 06:08 AM, Jim Felder wrote:
>      > About a month ago I wrote about having installed two pairs of USB
>     ports and
>      > an LED voltage display in my Vanagon. The round double outlet on
>     the dash
>      > took the place of my factory Eberspacher heater knob and the
>      > outlet-and-voltmeter combination set neatly into what was the
>     rear ashtray.
>      >
>      > That's when I noticed a drop in voltage that would flatten the
>     battery
>      > after a couple of days of being parked. Long story made very short, I
>      > discovered that it was my radio in standby mode that was draining the
>      > battery. I pulled the fuse to the radio on Saturday and this
>     morning the
>      > voltage is showing 12.9, exactly where it was when I pulled the fuse.
>      >
>      > The reason that this was unknown to me all this time is that
>     coincident
>      > with the addition of the USB ports the Vanagon was, except for
>     use of my
>      > wife's Prius, my daily driver had been the Vanagon. When I got a
>     TDI Jetta
>      > the Vanagon started sitting for days or a week at a time, and
>     that's when
>      > the problem showed up.
>      >
>      > I could wire the radio to the switched 12v circuit that no doubt
>     came with
>      > it, but then I would have to have the key on to listen to music while
>      > camping. Is anyone using a switch on the circuit, and if so how
>     was it done
>      > and how does it work out for you?
>      >
>      > Jim
>      >
>