Tail/Brake light indicator

[ramman]

1979 Special

I'm having problems with the Tail/Brake indicator light coming on even though both are working properly. When I turn on the ignition switch the light comes on but goes out when the engine starts (this may be normal). I'll take the bike for a ride and as I throttle up the light comes on then will go out as I throttle down or even out, but as soon as I twist the throttle again on it comes. After I've run the bike for awhile I can get the light to come on simply by revving the engine. I have cleaned and applied dielectric grease to every connector in both circuits that I can find but it's still doing it. Does anybody have any ideas about what's going on?

Thanks

 

[bloodthirstysystem]

sounds like your regulator might be bad. check the voltage at your battery. should be 12v at idle and 14v revving.

don't ride too far, you're gonna be stranded

 

[retiredgentleman]

It may just be that the fail indicator is doing its job. The tail light is powered through the light checker circuit, which monitors current flow to the tail light. If the checker circuit sees low current, it may mean the 1157 bulb is starting to fail. Just put in a new 1157 bulb and see if it returns to normal.

 

[ramman]

Checked the voltage at the battery and all is good. Will try the new bulb thing next however I have been told that it is wattage sensitive and needs to be exact in order for the checker to function properly. Any thoughts?

 

[650Skull]

the 78/79 models have the charging system hooked up to the Brake/Tail light fail safe warning light. Like an alternator light on old cars. Check out your charging system, Rotor,reg/rect as well as the advice given

 

[retiredgentleman]

The light checker expects to see 0.6 amps or 8 watts for a 1157 bulb. However, I have used a GE 1077 bulb which draws 0.4 amps or 5.4 watts. The light checker works fine with both types. So, actually the light checker can tolerate different wattage ratings.

What I know for sure is that the light checker will turn on the failure warning light, when the current flow drops down to 0.073 amps. That is what my LED tail/brake light now draws. I removed the warning bulb, as it's no longer of any use with the LED.

 

[ramman]

Well after closer checking I discovered that the voltage drops off from around 14V at 3000 rpm to 12 something at the same time that the light indicator comes on. I changed the voltage regulator and got the same results. As the engine warms up it becomes more difficult to get the voltage to increase with rpm's. Apparently I have a charging system problem but it's not the regulator. Can someone tell me the next most likely place to look?

Thanks

 

[650Skull]

test your rotor first then the stator, Plenty of info in the tech on how to do this and a couple of live threads are working on this at the mo.