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Topic-icon 1977 R100/7 Headlight Switch issues

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3 weeks 6 days ago #6370 by cameron
1977 R100/7 Headlight Switch issues was created by cameron
I bought higher bars, so I needed new switches with longer wires. The right side I found used, easy. Left side (headlight and horn switch) I bought a new one. My original has the dip switch to turn the lights all the way off, but they don't sell that one. The new one has two less wires. I wired everything up and the light won't turn on except the high-beam flasher when you push the paddle switch all the way down. I thought maybe the missing two switches were the culprit, and if I put a spare wire in to bridge the connection between where those two had been, the headlight turns on, but then when I turn off the ignition it stays on until I disconnect the battery.

My question is: does anyone have experience replacing an old-style headlight switch with a new always-on I need to wire things up differently? I haven't found anything online despite a lot of searching. I studied the wiring diagrams of the 77 vs the 78, when they changed to an always-on, but none of my messing around yielded a solution. Thanks!

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3 weeks 5 days ago #6375 by 8053
Replied by 8053 on topic 1977 R100/7 Headlight Switch issues
O.K., understand that this is a guess. Going by the wiring diagram, locate the spades on the headlight relay where the wires from the original on/off switch are attached and bridge these with a jumper wire. This should create a situation as if the switch were in the on position.

Of course, try this trick at your own risk. I have never actually done it and can not know for sure what will happen. Be prepared to de-energize the system immediately if the wiring catches fire.

The flash-to-pass function of the hi/low beam switch is wired hot thru the switch, and as such, bypasses the headlight relay altogether.

James Strickland, IL. Airmarshal

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3 weeks 5 days ago - 3 weeks 5 days ago #6376 by Wobbly
Replied by Wobbly on topic 1977 R100/7 Headlight Switch issues
If I understand your dilemma correctly...

Your solution may be as simple as making several "extension cords" for the original handlebar switches. Airheads use US-standard 1/4 inch spade terminals. If you'll make up 12 or so, 6 to 8 inch long #16 AWG wires and crimp a male spade on one end, and a female spade on the other, you'll be able to connect those to the end of the existing handlebar switch leads and route them into the headlamp shell.

You won't need to destroy any vintage component, re-wire anything to non-standard where you won't be able to use the stock wiring diagram, and as long as you plug color-to-color you'll be up and running in no time.

These fully-insulated 1/4" spade connectors are available from your LAPS or online. The US standard is to color-code them for wire diameter, and so you want the Red-ish ones for 16-18 AWG wire. Not the Blue or Yellow color. Be sure they are the "fully insulated" style.

Here's examples of the male and female crimps on a fuse lead

Hope this helps.

Don't hide 'em, Ride 'em !!
Last edit: 3 weeks 5 days ago by Wobbly.

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2 weeks 2 days ago #6433 by 13807
Replied by 13807 on topic 1977 R100/7 Headlight Switch issues
If your headlight stays on when the Ignition is off, then you "bridged" the connection with a constant hot 12 volt source, and that should be a red wire. You will need to connect the headlight relay's pin 86 to a green wire, as green is hot only when the Ignition is on.
Headlight relay pin 85 goes to ground or brown. Pin 80 goes to red (constant hot) and pin 87 to yellow black (high / low beam switch input voltage). The output of the high / low beam switch goes to yellow for low beam or white for high beam.

What colors are your extra wires and where do they connect?


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