Keeping dipped beam on with full beam

[MarkJ]

I'm going to be changing my headlight unit soon, it's a two projector unit - one projector is dipped the other is full. I'd ideally like to have them both on when I hit the full beam switch. Currently if I had dipped on and hit the full beam the dipped beam goes off and full comes on. You only get both filaments lit when you hold down the passing switch.

What would be the easiest way to keep dipped on when full beam is switched? Best way I can think of so far is to run a diode from the full beam wire to the dipped. Maybe open up the switchgear and re-solder some wires?

[Stelmer]

I'd go about this by rewiring the dipped beam, providing main and dipped are different bulbs.

I'd cut the current +12v feed, isolate it and instead run a new feed directly from the battery to a relay. I would use the sidelight feed to switch the relay. Make sure the wiring from the battery can take the current and include a fuse.

Others might have better ideas....

[Raffles]

The easiest method would be to simply install a fused relay from the battery live terminal to the dipped beam with the trigger wire for the relay linked into the main beam wiring. This method would eliminate any potential overloading problems with existing wiring, switches, fuses etc.
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A good loser will always be a loser.

[WetSparks]

Just a word of caution here, temperature.

Can your bulb stand the extra temperature by having both elements lit. Is your reflector metal and able to withstand the extra temperature. But mainly, is your front lens glass or plastic, you don't want your front lens melting do you!

[MarkJ]

Ah, it's a new headlight unit - the current one is 2x H4 bulbs, and I'm moving to two projector units with a H3 in both - one projector is dipped the other full. Both projectors are metal/glass

[Pete.]

More to the point you might over-heat the bulb.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Raffles]

H3 bulbs are single element bulbs so it is unlikely that they will overheat if dip and main beam are illuminated at the same time. What is mystifying to me is why your existing unit uses H4 bulbs (which are twin element) but only utilises one element of each bulb.
____________________
A good loser will always be a loser.

[WD Forte]

What bike and whats the generator output?
both lights on will almost double the current consumption
and it may be wise check the alternator/charging system can cope
with the extra load.

Lets say you have a standard 55/65W as low and high beams
Most bikes run at near 14V so they will take roughly 4 and 4.5 amps respectively
thats about 8.5 amps and higher wattage lamps even more
100+65 may need about 12amps
If your alternator is up to the job it may a not be problem
and the aforementioned relays would be well advised.

[WetSparks]

Of course you could always convert to HID lighting and halve you current demand whilst tripling your light output!

[Pete.]