Headlight via relays

Biondino Posts : 200 Join date : 2021-11-17

Don't know how much I gain on it, but I've routed the main current directely from the battery to the headlamp. Via a relay and a fuse, of course.
The thinking is to get more power to the lamp (and put less strain on the switches), and thus get more light out on the road.
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I made a harness going from the battery via a fuse to a double relay, which i mounted on a bracket where the right hand horn is fitted.

I then drilled a 10 mm hole in the headlamp bucket and made a new harness between the relay and the bucket. Two thicker cables going from the relay to the high and low beam, and two thinner cables going back from the original harness to the relay.
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If anyone thinks this makes sense, I can give more details...

Tiradritto Posts : 377 Join date : 2019-12-05 Age : 55

Bjor - I fear this may be a wasted effort.
I haven't done much on the GRiSO headlight circuit, but I suspect this effort will only duplicate what the factory already has installed as there is typically an interposing headlight relay controlled by the switch. This is because the switch contacts are normally not rated to handle the current being drawn by the lamp.

there are several headlight threads that address the weak head light mostly by replacing the either the entire lamp assembly or the lamp itself with LED.

but I am curious if what you are doing has any noticeable effect.

Biondino Posts : 200 Join date : 2021-11-17

You might well be right Chris.
I've done this on some of my older Guzzis, and they benefitted from it. But they had a different set up.
I couldn't quite figure out from the wiring diagram how it was done on the GRiSO, but found out that the cables to the lamp seem very thin and that it could at least benefit from thicker cables. So I did the conversion.
I have already a led-lamp installed, and have bought a JW Speaker that will go in once I have found a suitable bucket for it... This will however, most probably reduce the need for the conversion even more...?

Biondino Posts : 200 Join date : 2021-11-17

Chris W wrote:: Bjor - I fear this may be a wasted effort.
I haven't done much on the GRiSO headlight circuit, but I suspect this effort will only duplicate what the factory already has installed as there is typically an interposing headlight relay controlled by the switch. This is because the switch contacts are normally not rated to handle the current being drawn by the lamp.

Just took a new glance on the wiring diagram, and to me it looks as if the power to the lamp comes straight from the switch and not from a relay...
There might be something I'm overlooking, though. Maybe someone with more expertice than me on electrics could clarify? Would like to know... Wink

Tiradritto Posts : 377 Join date : 2019-12-05 Age : 55

just looked at the schematic and to my surprise, I see no dedicated headlight relay and both high and low beams are fed directly through the switch as you described.

Biondino Posts : 200 Join date : 2021-11-17

Chris W wrote:: just looked at the schematic and to my surprise, I see no dedicated headlight relay and both high and low beams are fed directly through the switch as you described.

So then the question is whether or not thicker direct cables will give any gain in light performance.
It don't get dark during nights until August where I live (too close to the polar circle and the midnight sun), but I will eventually try to find out Smile

Biondino Posts : 200 Join date : 2021-11-17

So, our electrical Guru Kiwi Roy has enlightended us again (see [You must be registered and logged in to see this link.] ):

Kiwi_Roy wrote:: ---------------------------------------------------------
I have added a pair of relays to several bikes, there's plenty of room in the headlight bucket for that. Sometimes you can use just one form C relay. Run either the existing H/L wires to power up the relay coil, you will still need the existing headlight logic relay though, yes it will make the headlight considerably brighter.
Power up the relay 30 terminal from the battery through a fuse, You might also tap into the main feed at the ignition switch and take advantage of an existing main fuse at the battery (23), I no longer have a GRiSO so I'm not sure which of the two feeds from main fuses (23) is the beefiest.
---------------------------------------------------------
Another Option
A typical LED headlight will be at full brightness anywhere between 9 & 30 Volts so if you find a nice H4 LED headlight bulb and use the standard headlight wiring, you can afford to lose a volt or two in the wiring, it won't effect the brightness.

This means that re-routing the cables to the headlight makes sence as long as we are using ordinairy light bulbs, but not as much if we are converting into LED.
Thanks Roy!

Fra Cristoforo Posts : 773 Join date : 2016-04-14

Did it make things brighter? Just wondering.

Nibbio Posts : 519 Join date : 2017-11-09

GuzziSteve wrote:: Did it make things brighter? Just wondering.

Yes, you will note a significant increase of brightness any time you eliminate the ity bitty wires to the dimmer switch and back.

Explanation:
Brightness of bulb depends on both voltage and current. The brightness depends on power.
Since we know that Power (P) = Voltage x Current = V I
So whether you increase the current or the voltage the brightness will increase.

However if you change from an incandescent bulb to an LED you lose the advantage of relays because a typical LED lamp operates on < 9 Volts for full brightness, if you look at the specs you will typically see a range like 9 - 30 Volts

» Electrical Connections / Relays (keep them corrosion free)