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Thread: 1976 R75/6 Electrics

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    1976 R75/6 Electrics

    Went for a ride today. After 20 miles or so with a couple of short stops, I am having an interesting intermittent failure. When I hit the brakes, the brake light does not come on but the generator light on the instrument cluster does. It goes out as soon as I let off the brakes. A part f the failure is that the turn signals do not work. At least once when I tried the turn signals, the gen light came on but not every time. Just as I was pulling in the drive, everything went back to normal. When I hooked up the battery tender in the garage it very quickly flashed that the battery was more than 85% charged so I am quite sure the charging system is working fine because I was running with the headlights. I will work on this and I am sure I can trace it down but maybe the same thing has happened to someone out there?

    Thanks,

    Chip

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    I wouldn't rely on the battery tender to tell you the health of your charging system. I've read too many times how they show green quickly when in reality the battery was shot. A battery tender is really only for topping a battery off or keeping it at a full charge state once fully charged by the bike's system. I would get a good voltmeter and put it across the battery terminals and read the voltage at idle and at say 3K RPM. Do that before and after a ride.

    It sounds to me like the battery is not fully charged and that using the brake lights pulls the battery down a bit which then creates the voltage drop across the generator light. The way I understand the electrical system, everything is pulled from the battery...ignition, running lights, horn, etc. The charging system's job is just to dump voltage/current into the battery so that the other parts of the bike pull it out. If the sudden draw of the brake lights causes the light to come on, something is amiss.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    I will give the system a checkup tomorrow. The battery is new, it starts the motor and the headlights were still on. The brake light did not light at all and the gen light came on brightly and off again as fast as it came on. As I pulled into the drive, everything suddenly started working normally again. There must be a loose wire or something tied into the brake light circuit (but how can that effect the gen light?). The gen light will "flutter" when the engine is at idle but it goes solidly off at around 1,100RPM+/-. I have a bit less than 100 miles since putting the bike back into service and this hit all of a sudden (and went away as fast).

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    Hmmm...just a thought. We're not confusing the generator light with the oil pressure light? The oil pressure light will be on briefly at engine start and then go out with RPMs. If you were very low on oil, stepping on the brake would cause the oil to shift in the pan, resulting in no oil to the pickup. Can you make the "brake" light flicker while stepping on the brake in the driveway? That would rule out the oil idea. But check the oil anyway.

    When did this situation start? Any recent work on the bike?
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    A bit less than 100 miles after a frame up overhaul. It is the generator light (red, not orange) and the oil pressure light is working as it is supposed to. One thing I didn't mention and it will be the first place I look; yesterday was the first time I rode with the headlight on. I have been riding with the parking light on for visibility but our ride yesterday was approaching sunset so I put the headlight on. The failure occurred shortly thereafter. I am thinking that the heat from the headlight may have melted something in the headlight shell. Whatever it is, is common to the brake light and turn signal circuits and that can only be a ground wire? Perhaps that is shorted to something positive but the (short) circuit isn't complete until the brake light circuit is activated? That would cause a dive in the voltage which would(?) cause the generator light to come on? Lots of questions! Thanks.

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    I just pulled the headlight and everything is fine in the shell. I will check the tail light shell next. There is a ground circuit common to the brake light and turn signals in there as well. Later today most likely.

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    I have managed to take this from an intermittent to a steady failure. Apparently by juggling the wire harness where it comes from under the tank up to the instrument cluster but truthfully, who knows. Here are the symptoms that I can see: Key on, no trouble lights on the cluster come on; Lights on, the speedo and tach illumination as well as the high beam indicator work, headlight and tail light (license plate illumination) work; When the breaks are applied, there is no apparent voltage drop so that rules out a short circuit?; Engine still starts and runs (until I took the tank off for closer examination); Battery appears to have plenty of power. It cranks the engine and runs the headlight. Prior to the trouble lights on the cluster going out completely, they would come on bright and would stay that way until I either hit the turn signal switch or the break. Then they would go out (or very dim) and stay that way. Once they came back up again (turning the key off or juggling wires would do this), I tried the same using the headlight switch. That did not kill the trouble lights. The lights came on and the trouble lights stayed lit bright. I have the wiring diagram but I am having a difficult time figuring out where to look! Any thoughts?

    Thanks,

    Chip

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    If it can get any stranger, it will. After twenty minutes or so (away from the bike), it is back to instrument lights on when I turn the key on, they go out or dim when I put the brake or the turn signals on and they come back up again after a short wait. I thought I had some reliable feedback fumbling with the wires to the right handlebar control (kill switch) but I couldn't get it to repeat more than once or twice.

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    Not for sure yet but it looks like the 8 amp fuse (Block 15 on the wiring diagram) while not blown, had sufficient corrosion, not visible at a glance, to permit only a small amount of current to flow. It would light the "dash lights" but not the brake light and would not power the turn signals. I cleaned the contact and on the center stand, all appears good. I'll go for a ride and tempt fate! That fuse is common to the effected components.

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    Problem solved. I guess the fuse was letting enough juice to flow to light the cluster lights but when asked to light the brake light it shut down. I guess that is where the generator light gets its signal voltage so when the brake light switch, or the turn signal switch were thrown, the signal voltage dropped way down and the light came on.

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    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    I wouldn't rely on the battery tender to tell you the health of your charging system. I've read too many times how they show green quickly when in reality the battery was shot. A battery tender is really only for topping a battery off or keeping it at a full charge state once fully charged by the bike's system. I would get a good voltmeter and put it across the battery terminals and read the voltage at idle and at say 3K RPM. Do that before and after a ride.

    It sounds to me like the battery is not fully charged and that using the brake lights pulls the battery down a bit which then creates the voltage drop across the generator light. The way I understand the electrical system, everything is pulled from the battery...ignition, running lights, horn, etc. The charging system's job is just to dump voltage/current into the battery so that the other parts of the bike pull it out. If the sudden draw of the brake lights causes the light to come on, something is amiss.

    Kurt,

    This has almost nothing to do with this particular problem, but can you recommend a voltage gage that I could purchase and install on my bike and place it in my Luftmeister fairing?

    Is this something that has to be motorcycle specific, or are there "generic" ones available that would work? Other than mounting to frame or in Fairing, is the the wiring simply just hooking one wire to neg. battery terminal, and the other wire to the positive battery terminal?

    Thanks ahead of time.

  13. #13
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    Jimmy -

    I had a Motometer in my Luftmeister when I got it but it went south on me. I ended up getting a VDO gage from NAPA...even considered something from Bass Pro Shops. You want something that has some damping in it, so it doesn't bounce around a lot. IIRC, the hole opening is 2-1/16".

    I ran my leads as you suggest...negative to a good frame ground (coil ground bolt as I recall) and the positive to the + battery post. This way I'm reading directly at the battery, not somewhere else in the circuit. I also used a switch in the positive side so I could turn off the meter when I parked the bike. Since I had access to aircraft-grade switches at work (the kind of the red guard that can be kept covered in the cockpit of the aircraft), I used one of those.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by jimmylee View Post
    Kurt,

    This has almost nothing to do with this particular problem, but can you recommend a voltage gage that I could purchase and install on my bike and place it in my Luftmeister fairing?
    I installed a Heads-Up Voltage Monitor on my nekkid R75/6. It is a single LED that indicates voltages from <12V to >15.2V with various colors. Flashing is bad, steady green is good.
    Justin in Somerville, MA
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    76 R75/6, 78 P200E, 63 VBB
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    Quote Originally Posted by stanley83 View Post
    I installed a Heads-Up Voltage Monitor on my nekkid R75/6. It is a single LED that indicates voltages from <12V to >15.2V with various colors. Flashing is bad, steady green is good.
    Is there any advantage/disadvantage of having a dial face volt meter as opposed to this one, with a color indicator light?

    Also, this one, were there just 2 wires to hook up one + and the other - ??

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