Heat-related brake light failure.

[Le_Blur]

I completely stripped and re-built my NC30 back in June. It passed the MOT shortly afterwards with no problems, and has provided me with months of trouble-free use until now.

During the re-build, I rewired the stretch of loom from the genny to the reg/rec with new connectors at either end and a 2005 R1 reg/rec. It also had a new battery. The loom was completely stripped and re-wrapped, and I replaced as many connectors with new as I could find replacements for. Any that weren't replaced were throughly cleaned. The frame was also cleaned, and I ensured all the earths had good clean connections. I thought I was pretty thorough because I'd had previous reg/rec gremlins.

So, now for the problem. It's an odd one. The bike starts on the button and warms up beautifully. The lights work fine and everything seems peachy. As soon as the temperature gauge starts to pick up and register a temperature, the brake lights flicker and then cut out. I also loose the speedo, tacho and temperature gauge lights, but not the idiot lights. The brake lights work if I depress either lever. After a short period of riding (10 mins or so) everything tends to come back on again. I've only tested this a coupla times as I don't wanna get a tug from the Old Bill for having no brake lights.

I've double checked the reg/rec and it's limiting the voltage when rev'd as it should, and seems to be providing a good charging voltage the rest of the time. I've tried a continuity check from the back lights, to the brown connector on the LHS, to the headlight subloom and everything seems ok. I must admit to only having checked the brown/white wire as, from staring at the Haynes wiring diagram for an extended period, it seems to be the only common link between the clocks and the brake lights. Can you tell I'm rubbish with electrics, yet?

Any thoughts, gentlemen?

[Le_Blur]

No takers? I could be on my own with this one, by the looks of it.

[speedy231278]

Ummm... maybe you've got something causing a short at a particular temperature? The only way you're going to find this is wait until the bike starts doing it, and measure everything. Or, you need to strip the loom again to see if anything is damaged that you didn't spot last time. Maybe it's a bad earth. Try cleaning up the loom earth point if it's dirty and see what happens?

[Le_Blur]

Thanks, Speedy. It's pretty much what I was doing already. I'm just having a bit of trouble decyphering the wiring loom. I've continuity checked one wire which seems fine, but I'm can't figure out the rest. I'll double check the earths, but everything was sparkling clean about 6 months ago (unless one's worked loose?).

[alexandervf]

Did you replace the fuse box?

I rewired the stretch of loom from the genny to the reg/rec with new connectors at either end

What size of wire did you use? Did you replace other wires from the loom?

[Le_Blur]

I didn't replace the fuse box, but I have checked the fuse and it's still intact. I used 18AWG wire to replace the 3 yellow wires from the generator to the reg/rec.

[alexandervf]

Then your best bet is if you focus on your charging system and may i suggest your stator in particular.

Measure with a multimeter all three yellow wires (setting it to the scale of AC Volts , 100 or 200 Volts AC depending on the multimeter) the output of your stator, measure with your bike at 5000rpm and at 1200rpm. Then measure with the continuity tester of your multimeter each of the three yellow wires for continuity to ground.

Before all that bring your bike to running temperature.
Hope this helped

[Le_Blur]

I think I may have tracked this down to a faulty connection on the coolant temperature sensor. I checked the resistance of the sensor at 80 deg C, and it was well within the specified range. Wiggling the loom around this area would make the dash and brake lights flicker. I've closed the bullet connector up a bit for a tighter join, and zip-tied the loom to the frame to help support it. Fingers crossed this is fixed now.

[amorti]

I think I may have tracked this down to a faulty connection on the coolant temperature sensor. I checked the resistance of the sensor at 80 deg C, and it was well within the specified range. Wiggling the loom around this area would make the dash and brake lights flicker. I've closed the bullet connector up a bit for a tighter join, and zip-tied the loom to the frame to help support it. Fingers crossed this is fixed now.

I suspect this would be a red herring. My money says you have a rubbed through wire somewhere in the temp circuit which is letting +ve in to the -ve loop, and shorting various things out.

If you're confident that the bike isn't overheating then try leaving the temp gauge unplugged at the radiator AND at the clocks, and see if it solves the fault. Then if it does plug things in one at a time til the problem returns.

If there is a rubbed wire it'll be something like near the headstock or anywhere it can rub or catch or be pulled too tight.

I have no clue how the charging system or your mods to it could be at fault, that would maybe be revs, but very unlikely heat related.

[Le_Blur]

The bike's a UK-spec model and the loom is squeezed between the back of the oil cooler and the frame on its way up to the lights. My mate kept pointing at this area, shaking his head and muttering stuff. Perhaps this could be the culprit? I'm gonna have a quick spin around on it without the fairings on tomorrow night and see what's what.