Topic: Saving Headlight Switch

[The Lone Builder]

I am about to use Hondaman’s suggestion to save wear on my CB400 headlight switch. I did the same mod on my 750 following his instruction to the letter. It worked fine, with the only issue being the space – or lack thereof – available for the relays in the headlight shell.

Since the 400 shell is smaller, I was a bit concerned about fitting everything in, so I got some mini-relays. In the process I saw some 5-blade relays that will either function as twin make/break or changeover.

Is there any reason not to use a 5-blade 30A changeover relay instead of two 4-blade 25A make/break relays?

There is also a 5-blade mini relay available rated at 15/25A.  Would this be OK?

[bryanj]

No reason not to use a 5 pole except it changes over when power is applied so the high low would need modifying and whichever filament you connect to the normaly on contact will be on with ignition.

As to size divide your hoghest bulb wattage by 12 and that should be a maximum of 60% of rated relay current for long life

[The Lone Builder]

Thanks Bryan.

I’ve just thought about it a bit more, and it wouldn’t work.

When I say “Save the switch” I really mean “save the contacts”; so I am trying to save the contacts on the RHS (On/Off) and the LHS (Hi/Lo). The RHS is common to both Hi and Lo circuits.

With only one relay - one input and two outputs – it is only possible to save one set of contacts. If this is the Hi set, then the current for Lo goes straight through the bike switches to the lamp, defeating the purpose. If the Lo side is saved, then the Hi current runs through the switches.

So two relays are required.

It’s good to think these things through; easier to fix then, if/when it goes wrong.

[bryanj]

Roughly what i was trying to say politely mate

[Bodi]

I assume you mean the hi/lo beam switch? You can use a "form C" relay with SPDT switching. Connect black wire power to the relay contacts common terminal, wire lo beam to the "NC" terminal and the hi beam to the NO terminal. Ground one of the relay coil terminals and connect the other to your hi beam wire from the switch, the lo beam wire from the switch is unused.

[bryanj]

But he wants to save the on/off switch as well