For Christmas, I recently bought my wife as many LED light conversions for her R65, so naturally, I figured I would buy all the same components for our other two airheads and give myself some LED conversion projects. All went smooth with the R65 and the R90/6.. but I am stuck on the 1978 R100RS.
I successfully replaced the instrument gauge with a Katdash unit, along with the LED turn signals with flasher relay and parking light they offer. I then updated the headlight with a Cyclops H4. All went well. The last and final challenge is the Beacon LED Brake Light. https://www.beemershop.com/product/ei-beacon-led-brake-light-airhead-70-78.html
I installed the appropriate equivalent on the other two bikes with no problem but on the R100RS, it appeared to be the second easiest of the three, but after the install, the front brake doesn't activate the light. Back brake, no problem, and all of the other lights work, no problem. Just the front brake lever.... not activating the brake light anymore.
In my research it looks like it can be the brake switch located under the tank. Either, the terminals need to be disconnected, cleaned and plugged back in... or replace the switch. Before I pull the tank, is there something that I am missing?
Anyone else have this issue and know how to fix?
My ‘78 (was RS) has had that LED tail/brake light conversion for many years. (Mine from Rick Jones.). My schematic (also from Rick) indicates that the brake light wire is green/orange stripe from both the front and rear brake switch. The two wires merge somewhere at the rear of the bike, but I don’t know where. Perhaps the lead from the front switch got left out when you made your connections. Big question is, was it working before the conversion? It’s hard to believe that your brake switch would just coincidentally develop a problem at the same moment.
Yes, the front switch is on the front of the master cylinder under the tank. It’s pressure activated, so I have to believe that removing it opens up the brake hydraulic system. That causes a bunch more work, so hope it isn’t the switch itself.
If squeezing the front lever doesn’t produce 12v on the green/orange wire at the rear of the bike, I guess I’d check under the tank. There should be two wires at the switch. A (green?) 12v power wire that’s hot with the key on, and the green/orange wire to the brake light. All sorts of checks can be made here. I’d jump 12v from the battery to the green/orange which should activate the brake light and verify my installation back there. Make sure the hot wire is hot with the key on. With the hot wire on the switch, squeeze the lever and verify 12v on the other switch terminal. Somewhere in all this, you should find the issue.
Ha! I said the brake light wire is green/orange stripe, well, I think it’s actually green/red stripe. My schematic is so old it’s fading.
PS: I hope you got it figured out.
PS#2: I also installed the Cyclops LED headlight bulb. Double wow, what a difference! I get comments on that headlight based on daytime running. Gets people’s attention!
I've also installed that same LED rear light panel on several Airheads from 1979 to 1988, all without issue. Some ideas...
• It's easy enough to test the switch with a Test Light... basically a probe with a 12V light in the handle. One of the wires at the front BL switch will be power (turned ON with the ignition sw), and the other will be the wire leading to the rear lamp. Clip the test lamp wire to a cyl head fin or Neg side of the battery. When the brake lever is pulled, you should see the lamp in the test light activated. These switches can get fouled if you have not been changing your DOT4 brake fluid regularly, but rarely give up completely. You can usually restore them with compressed air blown into the fluid orifice.
• Once the front BL switch proves good, you can move your test lamp to the wires inside the tail lamp cover, and do the same test there.
• As always on 40+ year old machines that were driven in all sorts of weather, connector corrosion has to be suspected. I highly suggest you treat each of the connector terminals with No-Ox-Id electrical compound. These terminals include ALL of the following: the 4 fuse terminals inside the HL shell, both front BL switch terminals, the front harness-to-rear harness multi-pin connector terminals (located near the battery), and then all of the terminals inside the tail lamp shell. The procedure is to unplug the connector, lightly coat the male terminal, and then re-connect. In the case of the fuses: remove the fuse, lightly coat both ends and re-install each fuse.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Did you figure this out? Curious what the problem was.
why is removing the tank on that year anything but trivial? are you using 1/4" fuel line without the washer trick?
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