Greg,
I have figured out a way to implement the low/high on/on concept
with ONE relay. I sent this to the net a large too. For the newcomers
Greg and I want the low beams to stay on whilst the highs are selected.
And in the event the Garda wants to chat (do they really have light
meters??), then we want to be able to just switch off the ignition and have
the lows turn off, back to legal light levels.
Here's how to do it! Connect a relay between the high and low lines
where the relay coil is powered by the high beam line. The switched side of
the relay starts at a node from the fuse box that is switched by the ignition
(heater fan, coil, wipers, fuel pump...) and ends at the low beam. Here's
the ASCII diagram:
Fuse Box >---------------------- |
(IGN Switched) |
|
sw1 / o-----------|-----(------------> High Beams
/ / sw2 | R |
Battery >--o o----o/ High | L o / normally
light /Low | Y o/ open
switch o-----------(-----|------------> Low Beams
|
C
O
I
L
|
GND
As you hopefully can see, when the low beam is selected the relay
is off and only the low beams come on. When the ignition and highs are
on then the coil energizes and the relay's "normally open" switch closes
to allow fuse box current to run over to the low beams. When you see flashing
blues in the rear view mirror, just kill the ignition after you have found
your registration, turned down the music, pounded the dash and put your story
toghether, "you see officer, these old british cars are really a handful,
and well even if the speedometer light worked the needle would fluctuate
about an incorrect reading..."
Even the prince of darkness can't screw this approach up, unless you use
Lucas relays! Good luck, and I'm going to start shopping for a
20 W relay! Thanks for the good idea Greg. As a parting shot, I think
that with this configuration that during daylight operation with the lights
off the "flash to pass" will bring on BOTH low and high, and should be
a lot brighter too.
- Skip
'72 B roadster (Daily driver)
'74 BGT
'85 BMW 524td turbo diesel
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