DRL/ Side light Load Resistors

[Darren198712]

Right I have had a search on a few forums and it is unclear what load resistor is used for what.

I have only found DRL's but it would be helpful if someone posts up Numberplate lights and front side lights too

DRL
led drl bulbs with resistors installed (pics)
Claims to use 25ohm 25watts on DRL's

LED DRL's finally
Claims to use 10ohm 25watts on DRL's

B7 Audi A4, S4 and RS4 LED Daytime Running Lights (DRL) | Nick's Car Blog
Claims to use 25ohm 10-15watts on DRL but in the picture he uses 15ohms 25Watts

How to fit LEDs to the RS4 B7 DRLs
does not specify

I was wondering if someone can post up what they have used?

Thanks
Darren

 

[Richardesty]

Personally I've used 10w resistors when replacing sidelight bulbs (one per bulb), 25w resistors for DRLs (21w bulbs - one per bulb) - just one of these for a pair of numberplate lamps - and 50w resistors for H11 fogs (one per bulb). All from eBay 'load resistor' search.

 

[Darren198712]

what would you use for the ohms though?

would these work for the DRL's on the A4 ?
25W 25OHM LED RESISTER CANCELLER Flashing Brake Light Side DRL Day Time Flasher | eBay

 

[Darren198712]

bump anyone ?

 

[PetrolDave]

what would you use for the ohms though?

Start by assuming that the LEDs take so little current you can ignore them when calculating the resistor value. Then apply theses two formulae:

Power = Voltage * Current

Resistance = Voltage / Current

Which means: Resistance = Voltage * Voltage / Power

So for the resistor you need to make sure that:

Resistor Wattage = same Wattage as the original bulb

Resistor Ohms = 12 * 12 / (Bulb rating in Watts)