Dectane LED's Problems

[DazN]

Hi,

Fitted my Dectane rear LED's the other day and so far everything was great, look superb.

Started the car yesterday and it beeped, "rear left fog light out", checked the light and it's out completely. Switched engine off and on again, error cleared. Did it again today with same result, switch off and on and it's OK.

It's not just the fog light, it's the whole unit.

Tested the voltage, fine, tested the old light, also fine.

Phoned Dectane and they said the lights are designed for left hand drive cars only, there's nothing I can do to get them working 100% with a RHD car. They said if I can live with it then fine, if not then I can return them for a refund.

I asked about re-wiring them but am told it's almost impossible?

Any ideas?

Thanks

[wellzieRS4]

my leds from bm town do it if i have my lights set on auto when i start the car, they are ok if i turn lights on manually and start car in off position

[DazN]

Ah that might explain it, I could have switched the lights on before I started the engine.

I could run long wires and swap the left and right over!!

[HYFR]

my leds from bm town do it if i have my lights set on auto when i start the car, they are ok if i turn lights on manually and start car in off position

+1

its not a big issue ... just turn off and turn back on again ... all good

[Timster]

Blimey... I'd just send 'em back and get a refund. You shouldn't need to start running cables to make something like this "work properly".
Go back to stock until you find something that works as it should.

[HYFR]

my leds from bm town do it if i have my lights set on auto when i start the car, they are ok if i turn lights on manually and start car in off position

+1

its not a big issue ... just turn off and turn back on again ... all good

i should say this only happens if its dark (i.e. the autolights sense the need to come on)

if when driving, it gets dark (or go through a tunnel) the autolights come on, there is no error

it really isnt an issue at all

[P_G]

+1 in normal daylight conditions no issue, only when the auto lights think it is too dark and send a pulse through on start up. It's a 2 second thing to switch auto ligths off and on again.

[adsgreen]

how is this anything to do with the fact the lights are LHD?

I could understand if it thinks the wrong bulb is out - ie "left rear bulb out" message for the right rear unit.

Personally this is caused by LED's taking fractionally longer to cold start than conventional bulbs so causing the problem when the lights are left in the on position when the bulb check routine activates. I'm sure the car does something different when checking bulbs on engine start than when you are driving.

[wellzieRS4]

my leds from bm town do it if i have my lights set on auto when i start the car, they are ok if i turn lights on manually and start car in off position

+1

its not a big issue ... just turn off and turn back on again ... all good

+ 1

[klauster]

same issue here, but like said above, only happens when my come home lights are on (ie. dark)

I still think its worth putting up with this tiny issue to have LED rear lights

[PetrolDave]

Personally this is caused by LED's taking fractionally longer to cold start than conventional bulbs.

LEDS start in a few millionths of a second, but conventional bulbs take a few tenths of a seconds to start - so that theory doesn't hold water.

[PetrolDave]

[i should say this only happens if its dark (i.e. the autolights sense the need to come on)

Winter is approaching when it will be dark when going to work, and dark when coming home - so this will be happening twice a day, which will get bl**dy irritating IMHO.

[HYFR]

not for me Dave ... i'll be driving a '61 plate TTRS to work and back til January, then a '61 S4 til March ...

[adsgreen]

Personally this is caused by LED's taking fractionally longer to cold start than conventional bulbs.

LEDS start in a few millionths of a second, but conventional bulbs take a few tenths of a seconds to start - so that theory doesn't hold water.

It's not the speed as such but the way they start up. On a cold start the DIS is looking for very specific bulb activation behaviour and LED's trip this. After starting the DIS seems to be more forgiving.

[PetrolDave]

It's not the speed as such but the way they start up.

Ahh, that's not what you said.

On a cold start the DIS is looking for very specific bulb activation behaviour and LED's trip this. After starting the DIS seems to be more forgiving.

Conventional filament bulbs are very low resistance on start up when the element is cold, as they warm up to their running temperature the resistance increases - that's why if you measure the resistance of a cold bulb and do the P=V squared over R calculation it appears to be a much higher wattage than it actually is.

LEDs normally have as high as possible a parallel resistor (to minimise heat and energy waste) and if this simulates the resistance of a warm bulb and not the cold resistance that will trigger the bulb failure warning.