Kday, making a harness to relay my headlights.
10-24-2006, 08:34 PM
#1
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Kday, making a harness to relay my headlights.
I need to know what kind of relays to get (using two, one for highs, and one for lows). I notice some people use the 30w and some use the 40w. Which one? I also need to know if I should get the relays with a diode or resistor or both? I'm thinking two HL87402 is best. Also, can I use the brown wire from the stock wiring harness to ground out the headlights or should I run sperate wires to the headlights for that?
TIA<ul><li><a href="http://www.rallylights.com/hella/Relay_Mini_SPST_12v.asp">Relays</a></li></ul>
TIA<ul><li><a href="http://www.rallylights.com/hella/Relay_Mini_SPST_12v.asp">Relays</a></li></ul>
10-25-2006, 04:16 AM
#3
Either 30 amp or 40 amp would be okay.
A 100 watt bulb draws about 100w/12v=8.5ish amps.
You can use the brown wire for the low side of the relay coil, sure. Run a fat new one for the lamps.
The diode serves to prevent the inductive spike caused by turning off the relay coil (the same principle ignition coils generate sparks by). Use the diode version -- better to avoid polluting your electrical system. The resistor does the same job, but not as well.
The reason all relays don't have the built in diode is because the contacts will open more slowly with the diode than without. This can cause a problem when switching large loads (contact arcing) and potentially some applications need a quicker switching time. But for headlights it doesn't matter. Use the diode one.
You can use the brown wire for the low side of the relay coil, sure. Run a fat new one for the lamps.
The diode serves to prevent the inductive spike caused by turning off the relay coil (the same principle ignition coils generate sparks by). Use the diode version -- better to avoid polluting your electrical system. The resistor does the same job, but not as well.
The reason all relays don't have the built in diode is because the contacts will open more slowly with the diode than without. This can cause a problem when switching large loads (contact arcing) and potentially some applications need a quicker switching time. But for headlights it doesn't matter. Use the diode one.
