Hi,
It is really very simple to wire a relay to be normally closed. You need
a double throw relay with a 12 volt coil. That means it will complete a
circuit to one terminal(or set of terminals) when not energized and it
will complete a circuit to a different terminal(or set of terminals)
when it is energized. If you only want to break one side of the 12 volt
supply you would need a single pole, double throw, 12 volt coil relay.
If you want to break both hot and earth you would use a double pole,
double throw, 12 volt coil relay. These, along with appropriate sockets
are available at most any electronic supply house(tv parts store), or at
many Radio Shacks.
If you decide to go this route, and need further assistance, e-mail me
and I will e-mail you a wiring diagram.
Regards,
Mark in MS
MSAWDEY@aol.com wrote:
>
> The trick will be finding a "normally closed" relay, so that it will open when
> energized by the backup light circuit. This rules out the usual headlight
> relays, which are normally open. May have to pull out the Mouser electronics
> catalog and look for a NC, 12V unit.
>
>
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