C5 HID install clarifications
08-13-2012, 10:28 AM
#1
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C5 HID install clarifications
I have spent many hours researching posts on HID headlight installations in C5's and would like to clear up a few misconceptions;
Some have suggested using lower power resistors than 55 watts. In resistors, watts refers to power handling capacity, i.e., how much power it takes to burn out the resistor. The 55 watt resistor gets VERY hot: any smaller power handling capacity would result in the resistor burning out quickly or even starting a fire. Resistor loads are measured in ohms. The purpose of adding load is to fool the computer into thinking that it has a heavy headlight power draw and needs to raise the headlights. Putting a resistor "in-line" (in series with the headlight) will increase resistance and reduce power draw and do the opposite of what you desire, so the resistor has to be installed parallel to the headlight circuit (between the headlight hot wire and ground) in order to REDUCE the resistance of the load, increase the power draw and fool the computer into thinking you have stock headlights. Some vendors advertise plug and play resistor harnesses as "in-line"referring to installation instructions rather than actual circuit modification, further confusing the issue. Some users have adding a small courtesy lamp in parallel with the headlight low beam circuit with the exact same effect as the resistor, but with light being generated along with heat. Lamps are excellent dissipators of heat. and are a good solution. If you use a resistor, you need to mount it to the frame with screws so the frame can act as a heat sink and dissipate the heat generated by the resistor. Only ONE resistor is required to send the appropriate load signal to the computer. I used a 6 ohm 50 watt resistor in parallel with the low beam headlight. I spliced in one end of the resistor just ahead of the ballast and used a ring connector on the other end of the resistor to attach to the ground post that the horribly engineered ground connectors are bolted to near the headlight motor on the passenger side. Now my headlights retract normally whether in high beam or low beam mode, and both headlights have the same intensity. Hope that helps clear up some confusion...
Some have suggested using lower power resistors than 55 watts. In resistors, watts refers to power handling capacity, i.e., how much power it takes to burn out the resistor. The 55 watt resistor gets VERY hot: any smaller power handling capacity would result in the resistor burning out quickly or even starting a fire. Resistor loads are measured in ohms. The purpose of adding load is to fool the computer into thinking that it has a heavy headlight power draw and needs to raise the headlights. Putting a resistor "in-line" (in series with the headlight) will increase resistance and reduce power draw and do the opposite of what you desire, so the resistor has to be installed parallel to the headlight circuit (between the headlight hot wire and ground) in order to REDUCE the resistance of the load, increase the power draw and fool the computer into thinking you have stock headlights. Some vendors advertise plug and play resistor harnesses as "in-line"referring to installation instructions rather than actual circuit modification, further confusing the issue. Some users have adding a small courtesy lamp in parallel with the headlight low beam circuit with the exact same effect as the resistor, but with light being generated along with heat. Lamps are excellent dissipators of heat. and are a good solution. If you use a resistor, you need to mount it to the frame with screws so the frame can act as a heat sink and dissipate the heat generated by the resistor. Only ONE resistor is required to send the appropriate load signal to the computer. I used a 6 ohm 50 watt resistor in parallel with the low beam headlight. I spliced in one end of the resistor just ahead of the ballast and used a ring connector on the other end of the resistor to attach to the ground post that the horribly engineered ground connectors are bolted to near the headlight motor on the passenger side. Now my headlights retract normally whether in high beam or low beam mode, and both headlights have the same intensity. Hope that helps clear up some confusion...
08-13-2012, 02:52 PM
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Umm, the required wattage depends on the ohms of the resistor. A 100 ohm resistor will draw about 142mA and be required to dissipate about 2W of power. A 5W resistor that can't dissipate 2W of power would be a real POS. All it would require is free air mounting so the heat can get away from the body. And this resistor would provide about the same load as a 2W corner marker bulb (which itself is dissipating 2W of power, not 55W of power).
Your 6 ohm resistor is required to dissipate 33.6W of power. You should be hesitant when using a 55W rated resistor for that much power if you're not considering the proper mounting and heatsinking and airflow for the resistor.
Your 6 ohm resistor is required to dissipate 33.6W of power. You should be hesitant when using a 55W rated resistor for that much power if you're not considering the proper mounting and heatsinking and airflow for the resistor.
