More Divvy electrical woes. Brake light failed.

[krebsy]

Right, this is starting to get a little on the annoying side...

My brake light is working intermittantly on my Divvy 600 and I really need a hand with this. I have checked the bulb and socket and that appeared fine. The yellow cable from the "Big black box TM" (what is it BTW? Newbie question I know but the Haynes doesn't mention it) next to the fuse box through the loom and to the rear light socket seems to give intermittant 0 to total resistance. I bypassed that yellow wire with a spare length of cable but still no joy. I've tested the rear switch to the connector block for the lights and that appears fine. I've also tested the socket to the connector block and that's ok as well.

I guess the yellow cable might have gone rotten (I have just bypassed a length of my ignition circuit a few weeks ago) so I guess it's another night in the garage testing and splicing. I'm worried though that even after I shoved in a bypass cable (into each connector block) it still does not want to light up. I've a night time ride down the motorway tonight and I'm not relishing having to do it with dodgy lights.

Any Ideas? I'm thinking of simply ripping out the loom as a whole and replacing it. Is there anything else that could be dodgy that I need to check? The rear pedal and the front lever both fail to light up the brake light. All other lights (bar a duff auxillary bulb connection in the speedo) are fine.

Ta,

K.
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[krebsy]

Ahh. it's the igniter unit. No wonder there is no electrical connectivity... . (*slaps head*).(and good job I didn't put a bypass cable in...)


Ok, Still got the connectivity problem though with the lights working very intermittantly. The lights failed this morning, then I took off the seat and waggled the cables a bit. It worked. Then I put the seat back on the bike and it failed again. The connector block is WD40'ed up with no hint of corrosion though so bar chopping into the wiring loom again, I'm at a loss...
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[mchaggis]

Look for loose connectors, short circuits and bare wires pressing things they shouldn't be. In particular if it uses bullet connectors anywhere along the path to the light, look for oxidised (green for copper) wires inside those. It sounds as though putting the seat down puts enough pressure on the wire to pull something loose or push it to touch something else. It's also not impossible that a wire has snapped or frayed through within its insulation.
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[krebsy]

Ta,

Whilst there's still some light, I'll go and have a look. I think I can narrow it down to either the rear section to the light or the front to the switch. If it's the front then it's stanley knife to loom again...

K.
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[stinkwheel]

Sure the switches are working properly? They commonly fail.

Spade connectors sometimes become 'loose' after a time, pull the blocks apart and have a good look, you sometimes just need to bend the edges in a bit with some needle nose pliers.

Also make sure the ends of the wire are still securely soldered to the bulb holder (especially the 'earth' one on the outside of the holder).

Only then would I suspect the wires themselves. Give them a pull where they go into any terminals, you shouldn't be able to pull them out. If the wire is broken inside the insulation, you can sometimes feel it 'stretch' when you pull on either end.

In any case, don't chop any wires out just yet. Run a new wire paralell to the one you are suspicious of and see if that fixes it first. You should be able to check the continuity of the wires with a battery and bulb connected through it.

Remember, the current needs an earth too for the circuit to be complete. Rusty frame earths are a common cause of intermittant brake light/ indicator faults.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[bish777]

im currently replaceing rotted switches front and back-they're cheap enough.
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[Gazdaman]

I've seen several wires that look perfectly good have infinite/very high resistance just for the fact they're broken inside the insulation.

I'd just bust out a multimeter, and check everything until you find the problem. It's simple, there's no trick to it. You just need to trace it back until something doesn't add up.

I'd be trying the bulb first of all, then the switch, then any fuses, then I'd start checking continuity in wires until you find a break, then trace it back to somewhere more specific.

Gaz

[krebsy]

Well, i could not get it working after fettling about with it but it started to work the moment I put the seat back on the bike and sat down. Then it cut out again and I whacked the rear light cluster in frustration (not that hard though) and it started working again.

fired the bike up ths morning and it wasn't working again. Had no choice but to ride it as some Cnut glued my house and car locks up on monday and the car is going into the shop today to get the locks changed. It seemed to be working in traffic (could see it reflected off number plates etc.) but had stopped 20 miles later.

Will check the rear cable section, starting with the earth, blue-red and yellow cables to the light socket, then will patch around the yellow cable and the connector block. The earth must be fine as the rear light is working fine, just the brake light...

K.
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[krebsy]

Appears to be a dodgy light socket. Will change it.

K.
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