Turn Signal turns four way flasher? - Triumph Forum: Triumph Rat Motorcycle Forums
Air Cooled Twins Technical Talk Technical Talk for Hinckley Triumph Twins: Bonneville, Bobber, T100, Speedmaster, America, Thruxton, and Scrambler.

Sponsored by: Triumph Twin Power Ltd

LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 03-23-2011, 10:49 PM Thread Starter
New Member
Production 125
Join Date: Sep 2010
Location: BC
Posts: 5
Turn Signal turns four way flasher?

Hey, I installed some new turn signals (British Customs) tonight, tested them as I installed each individually and all seemed to be working fine. I put everything back together and now if i switch the indicator left or right, both come on and flash. This does not make any sense to me. Any thoughts?
bcbonnie is offline  
Sponsored Links
post #2 of 4 (permalink) Old 03-24-2011, 01:57 AM
Lifetime Premium
Site Supporter
Main Motorcycle: 2009 Bonneville SE
Forchetto's Avatar
Join Date: Jun 2009
Location: Asturias, Spain
Posts: 19,567
Other Motorcycle: Yamaha XV1100
Extra Motorcycle: Qingqi QM200GY-BA
There are only 4 reasons why all 4 flashers can come on at the same time:

If the "live" side of either the front or rear lamps is shorted or somehow connected to the "live" wire that feeds the other side.

If the warning lamp or its holder are shorted.

A defective or disconnected ground on either the front or rear lamp set.

An internal short in the flasher switch.

My money is on the defective grounding. This is how the flasher circuit is wired:

Forchetto is offline  
post #3 of 4 (permalink) Old 03-24-2011, 02:08 AM
Super Moderator
Site Supporter
Main Motorcycle: Custom 955 Speed-Tona
DEcosse's Avatar
Join Date: Feb 2005
Location: Pleasanton CA
Posts: 19,442
It's not poor grounding - these are presumably LED turns I guess?
The reason all 4 come on is because of the OEM indicator lamp - this has much lower resistance relative to the now high resistance LEDs - so appears like a virtual 'short' path to the opposite side.

(The most simple test is to merely unplug your instrument connector plug or pull the lamp - if the turns then work normally, you have your confirmation)

The way the 'normal' idiot light works is:
The main current flows through the incandescent turn signals (Whichever side is selected by switch) to ground;
it also flows to a parallel circuit comprising (the indicator lamp (incandescent) in series with the opposite-side turn signals (incandescent)) to ground

The indicator lamp 'lights' because its resistance is much higher relatively (smaller wattage bulb) than the main turn signal bulb;
so proportionately more voltage is dropped across that indicator lamp than the 'opposite' main signal lamp (actually front & rear lamps in parallel) in series with it ;
so the indicator lights and the main lamp doesn't.
Now - when you install LEDs, they have very high resistance compared to the indicator lamp - so now the applied voltage is dropped over the LED turns as opposed to the indicator
- so both sides flash!
i.e. the indicator is now flashing on the opposite side because the higher voltage component in the opposite path is dropped across the LEDs, rather than the indicator bulb.
Hence the requirement to isolate that potential parallel path with diodes.

This is simplified diagram of how original indicator lamp functioned:

The solution is to do the diode mod for the indicator lamp

(note that on the Twins the negative for the high beam lamp is actually Brown I believe)

DEcosse is online now  
post #4 of 4 (permalink) Old 03-25-2011, 11:12 PM Thread Starter
New Member
Production 125
Join Date: Sep 2010
Location: BC
Posts: 5
I think you were right Forchetto. Pulled everything apart, took a little more care insulating the wires. Seems to be working fine now.

Thanks to you both for the insight.
bcbonnie is offline  
Sponsored Links

Quick Reply
All posts must adhere to Forum Rules

Register Now

In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Similar Threads
Thread Thread Starter Forum Replies Last Post
Turn Signal Flasher Don x 3 Trophy 7 01-22-2017 10:11 PM
turn signal flasher rick littleton Air Cooled Twins Technical Talk 18 04-10-2015 07:00 PM
Turn Signal Flasher Relay ArmyBonnie Air Cooled Twins Technical Talk 22 09-27-2012 06:24 PM
turn signal flasher rick littleton The Welcome Center 1 07-21-2010 10:37 PM
turn signal flasher help needed robadele Sprint Forum 4 07-24-2006 07:29 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

For the best viewing experience please update your browser to Google Chrome