How do you measure the draw?

Rob
vwrobb@gmail.com
On Sep 1, 2015 9:39 AM, "Larry Alofs" <lalofs@gmail.com> wrote:

> A lot of the speculation and contradictory "understanding" can be cleared
> up for any given radio by actually measuring the current draw thru the
> wires with the radio in various modes, on, off, high volume, low volume,
> etc.
>
> Larry A.
>
>
> On Tue, Sep 1, 2015 at 11:16 AM, Rocket J Squirrel <
> camping.elliott@gmail.com> wrote:
>
> > This page also seems to indicate that the fatter wire (the constant-on
> > wire) is the main source of power for the radio, and the skinnier wire
> > (switched) is only used to wake the radio up.
> >
> > <
> >
> http://avic411.com/index.php?/topic/36319-which-wire-is-the-power-source-yellow-or-red/
> > >
> >
> > "Without a doubt B+ (the yellow wire) is the main current carrying wire,
> > but this is only up to a point, as you have seen due to the radio fuse
> > not being more than about 10A typically on vehicles. Acc/ignition is
> > just a turn-on signal. While it can be used at a lower current
> > application, it is not typically meant for higher loads."
> >
> > --
> > Jack "Rocket j Squirrel" Elliott
> > 1984 Westfalia, auto trans,
> > Bend, Ore.
> >
> > On 09/01/2015 07:57 AM, Jon VO wrote:
> >
> >> Well, my understanding is a bit different; the ignition switch controls
> >> /switched/ power to the stereo, and is the source of the amplifier &
> >> control power which is usually multiple amps for a high-powered stereo.
> >> The other continuous power lead is supposed to draw only a few milliamps
> >> to keep the memory charged and for control functions, and is powered all
> >> the time. At least that is the way the stereos worked when the Vanagon
> >> was current. If you want to reduce the current through the ignition
> >> switch, you would need to add a relay, and I believe some newer vehicles
> >> already do this.
> >> Jon
> >>
> >> On 9/1/2015 8:45 AM, Rocket J Squirrel wrote:
> >>
> >>> 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
> >>>>      >
> >>>>
> >>>>
> >>
>