Bulb warning light on dash - MOT issue?

[LordRaiden84]

Hi all

My MOT is due near the end of December so wanting to ask this question now in case I need to do some adjustments.

Basically, swapped the standard rear number plate lights for LED and I have a permanent bulb error light.

These were aquired from a kind member on here who I might add, stated thete were no issues with his VRS.

I'm concerned my cars canbus system isn't compatible with these lights and am I right in saying that certain years of the VRS FL won't code them out?

The LED's btw are the Superskoda set so I'm suprised they have resulted in this.

Will this count as an MOT fail or just an advisory?

Will I have to put the original ones back in temporarily until after it's tested?

[mikey vrs]

Im sure ive read on here that some leds require a resistor adding or the original bulb used as well as the new led,my pre facelift vrs had led no.plate lights & they fitted with no problems,im not 100% sure ref the mot however if it was me id refit the standard bulbs for the mot until you can sort the issue correctly as a warning light on the dash would bug me... 

[langers2k]

I don't think it's an MOT fail but I'm not sure.

 

Depending on what BCM is fitted, you might be able to code the warning out. Otherwise, as Mikey mentioned, some people have piggy backed their existing bulbs or used resistors.

 

What year is it and do you have a VCDS scan?

[LordRaiden84]

It's a 2011 plate. I don't have the facility to do VCDS scan I'm afraid. I may have to go down the route of what mikey suggested and install the original lamps prior to it's MOT.

[Jevpls]

No idea about the MOT but I wouldn't live with such warning light on.

1) it's very annoying and it gives the feeling that something's wrong.

2) in case a bulb dies, you don't know that. You are used to the warning light and don't see that another bulb has failed.

[mannyo]

Why not just refit the original bulbs for the MOT.

[fordfan]

It's not a MOT issue, at the worst it'll just get an advisory.

[Muzza80]

Just fit these and be done with it, my 11 plate VRS couldnt be coded out for the rear bulb led error so I suspect as Mike says this was only available in BCM's in later cars.

 

http://www.ebay.co.uk/itm/252238066810

Edited 11 November, 2016 by Muzza80

[Tilt]

There are some (probably loads and cheaper than chips) led bulbs that do not cause a problem with the Canbus system. At least in mine, unless the rears or newer cars are different?

 

If you look at other topics re side light bulbs there are some links there.

 

I have had some in my sidilights for years without issue. Just changed them and a slightly different style (same as the mentioned link @ £3something for 6)

 

I have fitted one side so far to see if any difference in brightness between the two. No discernible difference.

 

Still no issues with Canbus system, and I know the system works as the first set I bought needed resistors, so I eventually used these for puddle lights (in the mirror).

Edited 11 November, 2016 by Tilt

[LordRaiden84]

Hi all

 

Just wanted to say thanks for everyone's contribution and I've decided to go down Muzzas suggestion and have ordered the resistors. Hopefully they will work without issues and the stupid warning will disappear, for good.

 

I feel this is much easier than messing around putting the standard bulbs back in or trying to 'piggy-back' bulbs onto the LED wiring loom. By the way, I appreciate peoples thoughts on a bulb warning looking wrong and I didn't realise that actually, it could be a safety issue if another bulb failed without my knowledge!

 

So yeah, thanks for pointing that out I can be a bit thick at times.

 

I will let you know how I get on. Thanks again peeps. This is exactly why this is a great forum and without you guys, sound advice would simply not exist

[RocheyDub]

Good advice people.

 

Newbie here, but mechanic by trade! I'm assuming a 5 watt resistor (of say maybe 10 ohms?) wired in would do the same job? Less likely to give grief than a standard bulb put in? Or am I talking through my hat?? 

 

I might try one and see how it goes. I'll keep you in the loop if I find it works!

 

Mine is a 2011 VRS.

[xman]

Power = V * V / R

So a 10 ohm resistor will dissipate 14.3*14.3/10 = 21watts

5w you would need a 43 ohm resistor. In practice with the led bulb taking say around 1w you would be better off with 56 ohm which would only sink about 4w. It would however need a power rating of at least 10w (i.e. ceramic wirewound) to stand a reasonable chance of not burning out quickly. Thats a physically large resistor that wont fit in the holder along with the led bulb and the resistor still get stinking hot, well enough to melt the plastic lens/holder.

Better to stick a bit of black tape over the telltale if you desperately need those led bulbs.

Edited 14 November, 2016 by xman