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Last Updated: May 01, 2012

Installing HAZARD switch

Some bike models especially those commuter bikes often do not have a hazard switch to alert other motorist that you are travelling the road with problem with your bike.

Photo shown is the common block diagram of a turn signal wiring, wherein, when turn signal switch is activated, it will blink the turn signal lights left or right depending on the position of the switch. Front and rear signal lights are just parallel on each side.

More often, riders needs and want to install a HAZARD switch so that when activated will flash all signal lights to alert or inform other motorist to take caution on following you, that maybe you have some sorth of problem and or you are on a convoy.

HAZARD switch is so easy to do if you just follow your own bikes wiring diagram, by taking the common block diagram above only four components will be installed to have a hazard signal function.

  • normally open push button switch
  • 2 pcs of rectifier diode (ex: 1n4002)
  • 3 pcs of stranded wire, prefer #18 AWG
  • and an electronic flasher like on this link universal led flasher for leds or bulbs
Hazard Switch connection
The turn signal flasher on the block diagram will be replaced by your electronic flasher, aftermarket and or the DIY mentioned, and just follow the add on components, and voila, you have now a hazard function. no need for rewiring your old system.


quico said...

Wouldn't be necessary to change the turn signal relay? For example, I have a 2 x 21w + 3,4w relay for 2 bulbs operation plus the dash light. Making this change wouldn't overcome the relay power and risking damagint it? I mean, with the warning on, it would be throwing 4 x 21w + 6,8w (4 bulbs plus 2 from the dash lights)

Nathaniel Berdan said...

quico, turn signal relay works by turning on and off the bulb, and the contact point inside take all the stress during on condition, 21 watts bulb consume around 1.7A of current on a 12 volt system, thus if your relay contact rating let us say of 1 Amp..then more or else, it will fail in due time and will produce dark spot due to spark being generated when the contact is closing.

with your current setup of 4x 21 watts alone that will be 84 watts. current will then be 7 amps already.

if your relay rating is 20 amps then it is safe.

quico said...

Thank you so much for your reply!
I've checked the relay, and it's not clear (at least for me) what is the amp rating.
The relay is this one:

The only inscriptions on the relay are:
TL-67 (maybe the 67 part is for the amps?)
12.8v (obviously the voltage)
85c/m (I know that this is the blinking rate, so 85 blinks per minute)
21w (2 + 3,4w) and this is the 2x21w plus 3,4w for dash bulb.
What do you think?

quico said...

What if I change all of the bulbs for LED bulbs e buy a plug&play relay like this:

Nathaniel Berdan said...

quico, is your first flasher still the original thermal flasher and the oem type that was installed by the factory?

If YES, then it will not be suitable for LED and a combination of bulb and led. it will not flash and instead shall give only a steady lit.

For the last comment you posted, probably it will work but have not try though and instead build my own electronic flasher for led and up to this date did not gave any problem.

quico said...

Yes, it is the original relay. Btw, it's a Suzuki Burgman UH125 scooter (2010 model).

By the pictures I posted, can you tell what is the AMP capacity?

My knowleadge in electronics is very limited, so if the original relay doesn't handle the 4 blinking lights at the same time, I think I'll buy that relay e give it a go with led's.
The only reason I'm considering the LED's, is because that relay in the ebay link is 60w max, so I conclude that it can't handle 4x21w bulbs.

Thank you so much for your help!

emil turallo said...

Why diode is heating up quickly when you use it