Electrical puzzle

[newmaac]

OK you electrical guru's, I could really use some advice.
1980 Special, with all stock wiring and fuse box.

I have lost power to the neutral lamp on the cluster, the turn signals, and maybe the gauge lights. At the same time, the tach dropped to a point where it reads less than 1000, no matter what the PRM range actually is.

I openened the headlight bucket this AM to check the connections, and everything seems as it should. (cleaned and greased them all about a year ago).
I checked the fuses and all are good. Then I put the key in and tried again.
When key was initially turned to the "on" position, the neutral lamp lit, so, I tried the turn signals. I heard a "click" that sounded like a relay. The neutral light went out and the turn signal didn't work.
So, I tried turning it off again to see if it (the neutral light) would come back.
It didn't.
I found that when I turn the ignition to "on" now, I can hear a relay click that I don't recall ever hearing before.
Before I take off the seat and tank and start "guessing", does anyone have a suggestion as to where to look?
I guess that the tach is the part that puzzles me the most. I know that there are white wires behind the fuse box that, when not connected well, can make the tach bounce, but I don't get why I would have a low, and inaccurate tach, while having other electrical issues.

Anybody??

TIA,
Mike

[newmaac]

I just went through Crazy Steve's trouble shooting overview and am still stumped.
A couple more facts though, to help pin point the problem.

I DO have headlight, both high and low beams.
I DO have the horn. (the horn is the only thing that I can think of that is not original. Years ago I added a big set of Fiams, and if I recall correctly, had to add a relay to the horn circuit, to handle the added draw)

[ViperRon]

I do not have my book here so I am going from memory but in the diagrams I think the Diode is inbetween and supplies the voltage there. Below is some troubleshooting information written up BY Crazy Steve and if you find its the diode it can be bought at Radioshack.

Headlight/instrument lights. Fed from the fuse panel (10 amp fuse) by a red/yellow wire to the lighting relay. Changes from a r/y to a blue/black after passing through the relay, then goes to the reserve lighting unit and the instrument lights (where it turns into a blue wire). If you have a bike that has the 'lights, on-off' switch on the right handlebar control, these two wires also go to that. On the switch, these are red/yellow, blue (not used), and a white which is connected to the blue/black. This is supposed to bypass the headlight relay where the switch is fitted. From the reserve lighting unit to the left handlebar switch, then from there to the headlight. Plug connections to check are at the relay, reserve lighting unit, and left handlebar switch plug under the tank. Note that the main wiring diagram for the '78-79 bikes has several mistakes in how this circuit is drawn, so go to the unit repair section for accurate info.

Alternator. All years have the same wiring from the coils; a brown and green from the field coil, and three whites and a yellow from the 'starter' coil. The field brown wire is tapped into the brown wire from the ignition switch inside the harness. The green wire goes to the regulator. On the other coil, the three white wires go to the regulator, and one is tapped to give a tach signal. On the '78-79 bikes, the yellow wire goes to the lighting relay to turn on the headlight when the motor starts. On the '80-81 bikes, the same white wire that goes to the tach is tapped and ran to the relay, with a in-line diode (exposed on the harness) and the yellow wire isn't used. These are the infamous plugs behind the fusebox that go bad...

[natemoen]

Have you checked the large white plug with the white wires on it behind the fuse box area? Check it, that often melts, clean and grease.

What is your battery voltage before starting the bike, at idle, at 3000 rpms?

[BA80]

It might sound silly but try unplugging the flasher cancelling unit. It's the only other thing I can find on the wiring diagram that shares a circuit with the light and tach.

[crazy steve]

...I have lost power to the neutral lamp on the cluster, the turn signals, and maybe the gauge lights. At the same time, the tach dropped to a point where it reads less than 1000, no matter what the PRM range actually is...

The key fact here is you have more than one circuit; the neutral light, turns, and tach all get power from the same source (the brown wire turn circuit), but the instrument lights are fed via the headlight circuit, so verify if the gauge lights are actually out. Do your 'other' bits fed from that brown circuit work, like the horn, brake lights, turn signals? No, you've got a bad connection at the fusebox. If yes, check the voltage at the brown wire in the headlight bucket plug and clean that connection or check for a possibly broken wire in the harness where it goes from the frame to the headlight. The one other thing both have in common is a ground wire, so check your ground connections in the plugs and particularly at the regulator mounting screw. A poor ground can do this....

[SFerinTEXAS]

natemoen Have you checked the large white plug with the white wires on it behind the fuse box area? Check it, that often melts, clean and grease.

What is your battery voltage before starting the bike, at idle, at 3000 rpms?
Today 12:16 PM

I'd go this way first. Is the headlight also not working?

[newmaac]

Thanks for the input folks.
BA80, It does look like it might simply be the flasher unit.
I removed the seat and tank so that I can get to, and clean all of the connections.
The "clicking" noise that I mentioned, was actually a relay, below the tank, up near the front tube, but also the flasher unit at the same time. This is the larger, 3 prong flasher that is below the fuse box. When I disconnect the flasher unit, I get the other gauge lights back.
I haven't tried starting it yet to test the tach, because I want to clean all the other contacts before putting the tank back on.

Crazy Steve, your trouble shooting overview is pretty awesome. Thanks for taking the time to help those of us that "don't understand that which we can't see" )

Mike

[cywelchjr]

Thanks for the input folks.
BA80, It does look like it might simply be the flasher unit.
I removed the seat and tank so that I can get to, and clean all of the connections.
The "clicking" noise that I mentioned, was actually a relay, below the tank, up near the front tube, but also the flasher unit at the same time. This is the larger, 3 prong flasher that is below the fuse box. When I disconnect the flasher unit, I get the other gauge lights back.
I haven't tried starting it yet to test the tach, because I want to clean all the other contacts before putting the tank back on.

Crazy Steve, your trouble shooting overview is pretty awesome. Thanks for taking the time to help those of us that "don't understand that which we can't see" )

Mike

Very unlikely to be the flasher unit. The flasher unit symptom is most likely just that, a symptom caused by something else, most likely wiring problems or problems with the fuse box, which is one of the most common problems with these bikes wiring wise after the wiring plug behind the fuse block plate. My guess given what I know of the flasher system, is that it's wiring that's causing the flasher to show the symptom, with said wiring problem possibly being the fuse box.

[fredintoon]

Hi Mike,
two things I don't see mentioned; does it still start & run? Does it still charge?
The Q & D charge test, does the headlight get brighter as you rev up?

[cywelchjr]

OK you electrical guru's, I could really use some advice.
1980 Special, with all stock wiring and fuse box.

I have lost power to the neutral lamp on the cluster, the turn signals, and maybe the gauge lights. At the same time, the tach dropped to a point where it reads less than 1000, no matter what the PRM range actually is.

I openened the headlight bucket this AM to check the connections, and everything seems as it should. (cleaned and greased them all about a year ago).
I checked the fuses and all are good. Then I put the key in and tried again.
When key was initially turned to the "on" position, the neutral lamp lit, so, I tried the turn signals. I heard a "click" that sounded like a relay. The neutral light went out and the turn signal didn't work.
So, I tried turning it off again to see if it (the neutral light) would come back.
It didn't.
I found that when I turn the ignition to "on" now, I can hear a relay click that I don't recall ever hearing before.
Before I take off the seat and tank and start "guessing", does anyone have a suggestion as to where to look?
I guess that the tach is the part that puzzles me the most. I know that there are white wires behind the fuse box that, when not connected well, can make the tach bounce, but I don't get why I would have a low, and inaccurate tach, while having other electrical issues.

Anybody??

TIA,
Mike

Point to ponder. Once you turned the signals on, turning the key off and back on did NOT turn the signals off, but only told the auto cancel unit disable the signal flasher on power on (the default), so if there is a problem with the circuit that feeds the flasher, it will keep happening each time you turn on the key. Try pressing the turn signal switch in while in the center position which turns off the signals, then turn off the key and back on with the flasher plugged in, and you might find that the lights come on again. However, you still need to fix the wiring problem with is most likely a connector and/or the fuse box (it could be both at the same time).

[JasonRedbeard]

The fact that the neutral lamp worked until you increased the electrical load (by trying the blinker) practically screams weak connection. I'm betting on a weak, loose, or corroded ground.

[Seabass Critt]

more electrical issues

I recently bought a 1980 xs1100 special that didn't run and had some electrical issues, most trouble i am having now is no spark, plugs, coils, wires and cdi are all new, i just bought a new spark advance but haven't installed it yet. when i turn the key on i have 0 volts going to the headlight, the tail light and front left blinker stays on, also the horn doesn't turn off, and the tach goes right up to 10,000rpms, (engine is off) after a while the tach will start to move around from to to 5 to 3 then up to 7 and so forth, what could be causing that? the fuses are all new and all have good voltage going to them. I am thinking that my stator may be bad? if its not that i am at a loss. can anyone help me?? thanks much!

[bikerphil]

when i turn the key on i have 0 volts going to the headlight

The headlight runs thru a relay which is triggered only after the bike starts. It gets it's trigger signal from the alternator. The tach also gets it's signal from the alternator. The stators very rarely go bad, most electrical issues are from poor/corroded connections and the glass type fuse box is a weak point.

[Seabass Critt]

The fuse box is brand new as well as all the fuses and there is 10 volts going through all 4 fuses, 12 volts on the battery and 11.5 going to the solenoid, what would make the tach fluctuate like that?? oh another thing, I have 2 stray wired disconnected in the same cluster that the headlight and blinker wires come from on the same end, a blue wire, and a purple wire. I havea service manual but it doesnt thow these coming out around the lights.