Use of LED Indicator lamps in Vehicles

[mightymouse]

Just a little background info on the substitution of LED lamps for indicators in vehicles - have had lots of questions on this at work so its a current topic.

In the "old days" the flasher cans fitted to cars was an electromechanical unit that used the lamp current to repeatedly heat and cool a bimetalic strip - making and breaking the circuit generating the flash. Flash rate was VERY dependant on the load current ( number and size of lamps ).

More recently, "electronic" flasher cans are the norm, these use electronice to controll the flash rate and are not DIRECTLY load dependant.

HOWEVER there is a "feature" of these electronic flasher cans that we need to know about - lamp failure detection. These cans are still load sensitive - if a bulb fails they switch to a high blink rate to alert the driver to this condition. Each flasher can has a 'rating' of number and size of lamps.

Given the much lower operating draw of LED systems it is almost certain that fitting LED indicators will trigger the lamp fail detection in flasher cans resulting in a high flash rate. Whilst this is still technically legal ( the fail mode obviously can't be illegal from the OEM ) it will draw unwanted attention to the vehicle.

There are two solutions to the problem - each with pro's and cons....

1/ Fit a load resistor to the system to draw extra current to make up for what isn't being used by the LEDS. Seems a shame to save power and then waste it again but...... This is a relatively simple solution for older vehicles ( like most of ours.... ) but can interfere with electronic systems in modern vehicles as the load is not distributed where the electronics expects to find it. In some cases it can even cause ABS fault codes etc etc..... somewhat surprising but a fact.

Unfortunately as the majority of the load current is now drawn by the extra resistor the lamp failure mode is no longer operative - loose an LED indicator and you won't know about it.


2/ Adjust the load sensitive characteristics of the flasher can. This requires some technical exploration of the actual can in the car but this results in the retention of the lamp failure mode for your LED lamps... a good thing. Once again not advised in modern vehicles as there may not be a flasher can - simply a "sounder" to generate the "click", or indicators may be network driven.

Anyone with modest electronic ability may well be able to identify the components in the can responsible for failure detection, in most cases its a single chip and a few resistors that control the flash rate. I would avoid fitting an adjustable resistor except during development as they aren't very reliable. Set the value and then solder in a fixed resistor. You now have the correct flash rate and failure detection.

So there it is... modern cars - leave well alone unless your absolutely certain of the effects - older cars, issues that can be solved via either approach without ongoing technical problems.

[cj!]

Fit a LED flasher relay:?:

http://cgi.ebay.com.au/LED-flasher-for- ... .m20.l1116

[mightymouse]

Its an option cj! - lamp fail indication is current dependant and that is entirely load dependant and varies with the mixture and size of LEDs / incandescent lamps fitted. Adjustment to actual load is the real solution if you want it done correctly -and as long as thats possible then its cool. Given the small current draw of LED systems, adjustment will need to be quite fine.
As some of us are only interested in replacing some of our indicators with LED's its a "shades of grey" situation.

All depends how much "fix" you want / need. I'm uncertian if the ADR's require lamp fail indication...... I think you would be very unlucky to get caught on that issue or even if an engineer / offical would know about it, but its another factor.

There's a real liability / safety issue involved if you don't have lamp fail on your indicators and you cause an accident......
But for those who want things by the book legal then you might be getting into interesting waters if your really really picky.

[cj!]

Thanks for the heads-up. I do believe that it is a requirement that the faulty indicator warning is functional.

I have a LED relay similar to the ebay one that I am going to try with mine so we will see how it goes. I'll report back when it's done.

[mightymouse]

Haven't had the time to read these but this is what i was quoted.

"AS 2809.1 & Adr 13, Clause 6.5.* & 9

Tell-tale
Operating tell-tale mandatory for front and rear direction-indicator lamps. It
may be visual or auditory or both. If it is visual it shall be a flashing light
which, at least in the event of the malfunction of any of the front or rear
direction-indicator lamps, is either extinguished, or remains alight without
flashing, or shows a marked change of frequency. If it is entirely auditory
it shall be clearly audible and shall show a marked change of frequency, at
least in the event of the malfunction of any of the front or rear directionindicator
lamps.
If a motor vehicle is equipped to draw a trailer, it must be fitted with a
special visual operational tell-tale for the direction-indicator lamps on the
trailer unless the tell-tale of the drawing vehicle allows the failure of any one
of the direction-indicator lamps on the vehicle combination thus formed to
be detected.

6.5.9. Other requirements
The light shall be a flashing light flashing 90 +/- 30 times per minute.
Operation of the light-signal control shall be followed within not more than
one second by the emission of light and within not more than one and onehalf
seconds by its first extinction. If a motor vehicle is equipped to draw a
trailer, the control of the direction- indicator lamps on the drawing vehicle
shall also operate the indicator lamps of the trailer. In the event of failure,
other than a short-circuit, of one direction-indicator lamp, the others must
continue to flash, but the frequency in this condition may be different from
that prescribed.

[JohnD]

This is not a reply on the subject but an attempt to contact "mighty mouse". I've been told your the man to speak to about what can be done to a Feroza. I'd like to speak to you. My phone number is (03)59751642 - (In case I'm not there when you ring, its got voice mail so if you leave your number I will ring back.)

[mightymouse]

Just a small postscript.....

Had a look at two "LED" flasher cans today.

One had "For motorcycle use only" on the packaging and the other had "Motorcycle Flasher Relay" printed ( small print ) on the case. Seems the manufacturers are covering their rear ends