78 Honda express wiring/tailight issues

Ive been battling with getting my tail light and brake light working since i picked this thing up. So i guess ill start from the beginning, of course when i picked up the bike it was running just fine but all of the light were blown out. I figured ok ill just go buy a new battery and replace the light bulbs easy! Shouldnt take long and wont be to expensive...needless to say here i am.

i replaced the headlight with a replaceable lamp, got new indicator light, speedo bulb and brake/tail light bulb. At the end of all of that only headlight works. As as i can see the wiring harness and all of the wiring is in great shape. The battery is new and holds a charge just fine. What should i look into next ? I drive this thing way to much not to have a brake light.

Re: 78 Honda express wiring/tailight issues

Jack Rutherford /

did tail light work at all after changes?

Re: 78 Honda express wiring/tailight issues

All lights and horn run off of battery. The headlight runs off magneto when motor is running.

Re: 78 Honda express wiring/tailight issues

Jason Majernik /

Also check the fuse.

Re: 78 Honda express wiring/tailight issues

Jason Majernik /

And make sure the battery is fully charged. Even new ones need to be charged prior to using.

Re: 78 Honda express wiring/tailight issues

How adept are you with wiring diagrams and a multimeter?

Re: 78 Honda express wiring/tailight issues

So i actually just got almost everything functioning properly minus the actual brake light. The tail light works once i turn the key but nothing happens when i hit the brakes. The bulb is good i just checked the filament. Currently charging the battery for kicks.

Re: 78 Honda express wiring/tailight issues

I topped off the cells and currently i am charging it just in case. That said i have everything working except the brake lights. Running lights work as they should once i turn the key but nada when i hit the brakes.

Re: 78 Honda express wiring/tailight issues

ive never used one but i think i could handle it if need be.

Re: 78 Honda express wiring/tailight issues

Jason Majernik /

I’d guess that you either have a bad brake switch or it’s not wired correctly. Seems odd that both switches are bad. You might want to open the headlight and check the wiring.

Are you also sure you put in the right bulb into the taillight? There should be two elements in it. Did you accidentally burn one out? Make sure you have the right bulb, inspect the elements in it or simply replace and try again.

Re: 78 Honda express wiring/tailight issues

This is an article driving me crazy as far as I can tell it looks like both philonous are fine. Trace the wiring back into the and it looks fine on the other end headlight it also looks all right. I've got a brand new bulb somewhere I just have got to find it just in case. I'm going to have to examine assembly very closely I guess

Re: 78 Honda express wiring/tailight issues

Jason Majernik /

I’d like to hear how it turns out. I’m out of suggestions at this point. Hope you get it working. These things drive me mad, too, but in a way that makes me want to understand them better.

Re: 78 Honda express wiring/tailight issues

Brake light is powered from battery too. Power comes from one or both of brake light switches on handle bars. Its unlikely both are bad or have an issue but possible. Get a multimeter and probe the brake light socket for voltage. Work your way back towards the battery from there. Its unlikely a ground issue since the tail light is working and shares the same ground. Also, there are (bullet) connections in the wiring from tail light assembly to wiring harness. Those are under the fuel tank above rear fender. Three wires, ground, tail light and brake light. Could be bad connection there. (edited)

Re: 78 Honda express wiring/tailight issues

So the wiring goes under the tank and into the bottom of the seat. right before it heads into the seat all of the wires are wrapped real well with electrical tape or something until it meets another taped bundle of wires and joins them. I havent yet peeled it all back and figured out whats going there but i will by the end of the day. Ill keep you posted to what i find.

Re: 78 Honda express wiring/tailight issues

Someone has taped the harness up. The tail light was made to be removed if damaged. You can see two of the three bullet connectors in this pic and gives you some idea as to how far away from the light the connectors are. You should be able to feel or see the lumps under the tape.

Screenshot_2020-11-29-08-59-00.png

Re: 78 Honda express wiring/tailight issues

Yes sir, found them pretty easily. Cleaned the connections best I could and no change. However I did try and reverse the brake grn/yellow wire and brown wire to see if there was a mix up and the light powered on still but brake light still didn't work

Re: 78 Honda express wiring/tailight issues

So this is what I found underneath the seat and coil/condenser. Looks like the the ground was spliced together? Haven't found a multi meter yet unfortunately. I guess I'm going to chase it into headlight and see what's going on a bit closer

20201129_165209.jpg

Re: 78 Honda express wiring/tailight issues

So i finally got things figured out. It took me forever but i finally bought a multimeter and started to test everything. The right hand brake switch is shot but the left was good. as soon is is disconnected the right hand brake from the circuit and tried to use the left hand brake the brake light worked. So that right had brake was causing the the entire issue. I don't quite understand much about wiring yet so im still baffled. I thought that each brake was independent of one another and if one failed it wouldn't effect the others function. Either way im real happy that its working in some capacity.

Re: 78 Honda express wiring/tailight issues

Jason Majernik /

Glad it’s better! I had issues with a bad brake switch on an NC50. The wiring in it must have been shorting out, and it blew the fuse twice. After I replaced it, I no longer had any issues. Wiring gremlins, man.

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