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Technical Side light bulb wattage rear end

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Technical Side light bulb wattage rear end

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Puntoproud

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Hi Guys n Gals , I've just fitted new rear lights to my Punto that are basically clear lens instead of the factory coloured ones(they look nicer) .. problem is that they specify 5W maximum for the sidelight bulbs which illuminate fine but being only 5W - they are throwing up a bulb failure on dash!! Will it make much heat difference if i use 10W bulbs ??
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considering i tend to drive with sidelights on as much as possible (always have, always will for safety)

atvb

Puntoproud
 
But the electrics is standard and will always generate an error if the resistance of the tungsten wire in the bulb installed will be smaller than the one that should have been installed.

Tungsten wire bulbs transform much of the electric energy into heat. And only a part into light (the internet says around 5%). I don't know if we can assume that a 10W bulb will generate twice as much heat as the 5W bulb, but it will be close to it.

You have several choices:
  • install a LED instead of a tungsten wire bulb. I think that your Punto has CAN, so you'll need a LED that will not generate the same type of the error (safe for CAN, or different depending on how the producer calls it). I don't know how it is concerned in the UK, but generally the lamp is homologated (= road legal) in its entirety (= lamp + light source). If you change one of these, the homologation is void. In fact that could also be the case with your aftermarket lamps. No idea if they have a homologation. It shall be marked on the lamp. Some producers (especially from China) put homologation marks without having the homologation done;
  • use a 5W bulb, in theory safe for the lamp, but less visible. To avoid the error, you should add a specific resistor (the best I think would be on the side light wire just before the lamp). To calculate the right value you should check the resistance of the 10W bulb, substract from it the resistance of the 5W bulb. That will fool the CAN system in the car but should do nothing to the bulb / light. Resistors generate heat, too;
  • use a standard bulb as per manual (10W) and hope that it won't burn the plastic of the lamp;
  • revert to the original light :)
 
the green vanper said:
But the electrics is standard and will always generate an error if the resistance of the tungsten wire in the bulb installed will be smaller than the one that should have been installed.

Tungsten wire bulbs transform much of the electric energy into heat. And only a part into light (the internet says around 5%). I don't know if we can assume that a 10W bulb will generate twice as much heat as the 5W bulb, but it will be close to it.

You have several choices:
  • install a LED instead of a tungsten wire bulb. I think that your Punto has CAN, so you'll need a LED that will not generate the same type of the error (safe for CAN, or different depending on how the producer calls it). I don't know how it is concerned in the UK, but generally the lamp is homologated (= road legal) in its entirety (= lamp + light source). If you change one of these, the homologation is void. In fact that could also be the case with your aftermarket lamps. No idea if they have a homologation. It shall be marked on the lamp. Some producers (especially from China) put homologation marks without having the homologation done;
  • use a 5W bulb, in theory safe for the lamp, but less visible. To avoid the error, you should add a specific resistor (the best I think would be on the side light wire just before the lamp). To calculate the right value you should check the resistance of the 10W bulb, substract from it the resistance of the 5W bulb. That will fool the CAN system in the car but should do nothing to the bulb / light. Resistors generate heat, too;
  • use a standard bulb as per manual (10W) and hope that it won't burn the plastic of the lamp;
  • revert to the original light :)
Click to expand...
I don't know what difference it makes (apart from alternator putting 14v in ) but I checked the nsr wiring plug and the earth connection was bent but working, so I straightened the terminal and reconnected. Then turn ignition to check lights...no bulb failure light !! ... I then started car and bulb failure light came on ?? . The ONLY LED bulb is my reverse light, but would that throw up an error when not in use? It didn't the previous week when I had the other light clusters fitted !! 🤔 confused.com(pletely).
Ps:thanks for your help so far 😉

Atvb

Puntoproud
 
the green vanper said:
Put a 10W bulb to check :) That's the easiest way to get the answer :)
Click to expand...
Thanks , I tried that but still coming up on dash ! Another thing I've thought of is the last pair of custom lights I had used identical bayonet fitting bulb holders but the wiring is a thicker gauge- could this be the cause of the less resistance in the new lights? ... I shall swap out the light , plug up the old one and see if the problem goes- if so - I'll just switch over the wiring harness from the old light cluster to the new one 🙃,I'll keep you informed, thanks again for following my journey 😁🤟

Atvb

Puntoproud
 
the green vanper said:
I'm 100% sure there should be some tolerance on the readings, but yes, that could also be a problem.

Is it specified on the dashboard which bulb is defect? if not, check the others, perhaps by coincidence there's another one blown :D
Click to expand...
That was one of my first thoughts too, I check them every time I go to make adjustments on this issue . As for specific bulb identification- it's a mk2 punto!!- I'm surprised the bulb failure bulb hasn't failed yet 😁

Atvb

Puntoproud
 
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