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Brake light flashes when indicators on

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scotto75
Renault 5 Driver



Joined: 13 Mar 2016
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PostPosted: 22:20 - 11 Sep 2019    Post subject: Brake light flashes when indicators on Reply with quote

Hi,

I am trying to get a '80 6V CG125 ready to be sold and have a small issue with the indicators. They work fine on their own, but when the brake light is on, the indicators are non existent and brake light flashes instead.

The 12V feed for the indicator circuit starts from the ignition switch where, inside the headlight bowl, it splits off to the indicator relay, the brake lights switches and the neutral light in the speedo. From the relay it goes to the handlebar switch and then off to either pair of indicators, and also the warning light in the speedo.

The indicators are those single wire types where the circuit is grounded through the casing of the indicator making contact with the frame via the thread. It is also grounded at the speedo idiot light through the opposite indicator circuit not in use. Would this assumption be correct?

I am assuming that it is poor grounding on the indicator circuits that is the root cause. The 12v feed to the indicator relay is finding its way down the brake light circuit as the current is flowing quicker along that path due to the crap grounding of the indicator circuit.

This method of wiring seems pretty common, and as I have had several Hondas from the 70's/80's I know that this isn't just 'one of those things' you have to live with, but as I'm selling it I don't want to spend a load for money and time trying to resolve it.

The solutions I have to resolve this are.....

1 - Connect a ground wire to the bulb holder inside each of the indicators.

2 - Solder a diode onto each side of the indicator circuit going to the speedo bulb, effectively making the current flow one way, and connect both left and right circuits to one side of the bulb and a dedicated ground to the other terminal.

3 - Having soldered diodes it would also be possible to fit 6V LED bulbs and a flasher relay, reducing the load on the indicator circuit but hopefully allowing other road users to actually notice the indicators are trying to flash.

My questions are whether I am missing anything, such as finding a way to separate the indicator circuit from the brake/neutral light... etc and whether the above ideas would help to solve the issue??

Any help or advice would be greatly received.
Thanks,
Scott.
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Honda ‘73 CB350, ‘80 CG125, ‘88 CG125, '73 Triumph T140V
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 01:15 - 12 Sep 2019    Post subject: Reply with quote

Thinking Thinking Thinking Thinking Thinking Sleeping
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scotto75
Renault 5 Driver



Joined: 13 Mar 2016
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PostPosted: 06:43 - 12 Sep 2019    Post subject: Reply with quote

jaffa90 wrote:
Thinking Thinking Thinking Thinking Thinking Sleeping


Aah, it must be very tiring for you trolling the internet in the early hours of the morning. I hope you got a good nights sleep and weren’t up too late 🛏 😴
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Islander
World Chat Champion



Joined: 05 Aug 2012
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PostPosted: 09:04 - 12 Sep 2019    Post subject: Reply with quote

Just fix the dodgy earth. Thumbs Up
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 11:48 - 12 Sep 2019    Post subject: Reply with quote

jaffa90 wrote:
Thinking Thinking Thinking Thinking Thinking Sleeping


As much as I hate to say it, I'm with Jaffa on this.

Sticking diodes in will just cause both to stop working because your problem is, as islander says, a bad earth.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 12:14 - 12 Sep 2019    Post subject: Reply with quote

It could also be a case of straight-up lack of power.

It might be simply that there isn't enough power in the battery to light up both flashers and the brake light. So the flashers land up dull and the brake light flashed brighter as the indicator bulbs stop drawing power.

Earthing may also be part of the problem. The back end of the bike isn't very well connected to the frame, it earths to the frame through the rear mudguard mounting bolt. This will be pretty rusty by now. Running a proper earth wire back to the frame/battery is a good idea.

The brake and flashers rely on the battery power but the charging system is very weedy, especially if you ride with the lights on all the time.

LED flashers would be a good idea. You don't need to piss about with soldering stuff on though, fit direct replacements and an electronic flasher relay.

The stop/tail light is more tricky. You'd need to get a very good quality one suitable for a POSITIVE EARTH. This is because the taillight part runs on AC and the brake light part on DC. The trouble may be that there isn't a clear difference between the stop and tail lights if you do this and you have to go back to an incandescent bulb.

I had similar problems with my wifes YB100 and overall weediness in charging was a lot of the problem. The bike simply wasn't designed to be ridden with the headlight on all the time, the headlight steals half the charging coil output.

I initially "fixed" it by fitting 5w bulbs in the flashers. These were actually brighter than the standard ones. As LEDs came on the market, I fitted those which totally fixed the problem.

I get oddball LED bulbs (like a 6v, positive earth stop and tail) and electronic flasher relays from https://www.classiccarleds.co.uk/
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chris-red
Have you considered a TDM?



Joined: 21 Sep 2005
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PostPosted: 17:19 - 12 Sep 2019    Post subject: Reply with quote

stinkwheel wrote:
It could also be a case of straight-up lack of power.

It might be simply that there isn't enough power in the battery to light up both flashers and the brake light. So the flashers land up dull and the brake light flashed brighter as the indicator bulbs stop drawing power.

Earthing may also be part of the problem. The back end of the bike isn't very well connected to the frame, it earths to the frame through the rear mudguard mounting bolt. This will be pretty rusty by now. Running a proper earth wire back to the frame/battery is a good idea.

The brake and flashers rely on the battery power but the charging system is very weedy, especially if you ride with the lights on all the time.

LED flashers would be a good idea. You don't need to piss about with soldering stuff on though, fit direct replacements and an electronic flasher relay.

The stop/tail light is more tricky. You'd need to get a very good quality one suitable for a POSITIVE EARTH. This is because the taillight part runs on AC and the brake light part on DC. The trouble may be that there isn't a clear difference between the stop and tail lights if you do this and you have to go back to an incandescent bulb.

I had similar problems with my wifes YB100 and overall weediness in charging was a lot of the problem. The bike simply wasn't designed to be ridden with the headlight on all the time, the headlight steals half the charging coil output.

I initially "fixed" it by fitting 5w bulbs in the flashers. These were actually brighter than the standard ones. As LEDs came on the market, I fitted those which totally fixed the problem.

I get oddball LED bulbs (like a 6v, positive earth stop and tail) and electronic flasher relays from https://www.classiccarleds.co.uk/


This^

I had the exact same issue on my 6v RXS 100

Cost me less than a fiver to fix buying a 6v LED flasher and bulbs on ebay.
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 18:08 - 12 Sep 2019    Post subject: Reply with quote

Tell a buyer it's a feature
'issa classic innit mate'
'can't buy them in the shops' sort of thing
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steve the grease
Crazy Courier



Joined: 26 Jan 2018
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PostPosted: 17:34 - 17 Sep 2019    Post subject: Reply with quote

The earth is Donald. The current path goes through the indicator , it can't find earth so it goes through brake light filament the rear light filament, along the wiring to the front light filament and then down to earth in the headlight . Run a simple wire from under the seat/ battery -/ wherever thats earthed to the rear light unit. The indicators are very dim as they are only dropping a couple of volts.
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