This DIY Volvo LED headlights post in now four years old, so here’s recent info with new methods and LED bulb hardware that addresses various successful and unsuccessful methods:
darrylrobert » I used this guys but fine tuned it by using very small resistors to allow the bulb out feature to remain working. I also was not able to get the turn signals to work using this method, i did experiment with a variable resistor and could pinpoint the exact spot that triggered the fast flashing/normal flash but found this changes with heat making it very difficult. I’ve ended up using LEDs on the back with built-in resistors, they were too bright for me so i partially covered them with a aluminum tube (been working well for 12months).
I’ve had to modify (add resistance) to nearly all my LEDS except the expensive Osram ones, they are all too bright.
volvodriver1 » I’m actually also trying to do the same with my headlights but I installed a wiring harness to power them and that’s really messing me up. The harness (with built in relays and in-line fuses) supplies the power to HIDs directly and only uses the factory headlight sockets to power the relay. I think this means that proper resistance readings within the CEM’s parameters via the shunts won’t even be possible. I was told that measuring in the milliohm range takes specialized equipment so its a matter of trial and error if I want to get this to work.
I dabbled a little but by severing the bridge between leads 2 &3 and soldering a resistor into place but the resistors I had laying around wasn’t built to dissipate the amount of heat it was giving off so the resistors went up in smoke. I’ll try to get my hands on some wire-wound resistors and give it another try.
@darrylrobert What value resistors were you using in your experiments?
darrylrobert » I haven’t converted my headlights, yes a multimeter wont measure that small a resistance.
For the shunt resistance, which i believe is what you need to modify ive heard that the resistor to use on the shunt is very small, i would try 0ohms to 0.5ohms, i also experimented with long lengths of different type of wire. I’m using resistors of 0.5ohms 1/4watt on each side of the shunt for parkers and brake LEDs, the more resistors you add in parallel the smaller the resistance becomes.
Adding small resistors to the shunt creates zero heat because its inline, where as adding resistance across pos/neg (load resistor) creates heat.
ndphotonl » For the headlights, you only need to to the drilling modification for the shunt in the front. I have been running LEDs in projectors for quite some time (on my S80). Highly recommended btw.