Radio Code

[Huw Powell]

> You can make one for about $3 at radio shack.  Get a cigarette lighter plug,
> and a 9V battery plug.  Connect them together...
> Before you disconnect the main battery, stick this thing into the cigarette
> lighter, then unhook the main battery.  It will provide just enough power to
> keep the radio (and ECU) settings.  Couple of warnings:  Make sure you
> unhook the main battery promptly after you plug in the 9V battery.  Also
> never forget to remove the 9V battery after reconnecting the main battery.
> You don't want them both plugged together for long because the 12V main
> battery will attempt to "charge" the 9V.

Putting a diode in the doohickey you are making will prevent this
reversed current flow, which, as you point out, would be very bad for
the 9 volt battery.  1 amp diodes are pretty cheap at RS as well.

Another minor warning, be careful to avoid turning anywthing on in the
car while this is set up, if you pull that 9v down far enough you'll
lose the radio anyway.  Not sure if the 9v battery has enough oomph to
run the interior light(s), door chime, etc.

--
Huw Powell

http://www.humanspeakers.com/

http://www.humanthoughts.org/