Can someone explain how this headlight wiring diagram works?

http://img86.imageshack.us/img86/33/headlightrelaywiringdiarb5.jpg





I would like to know how each part plays a role from beginning to end?Can someone explain how this headlight wiring diagram works?
This circuit is not a very good example of a headlight circuit because the high and low beams of the right and left side get their positive via a single fuse. This means that if there is a fault at any one of the lights that will cause the fuse to blow then all the lights will be dead. This is dangerous because when a fault occurs while you drive at speed then all the lights will go out. In some countries it is illegal to wire lights like this.





The circuit works like this:


The black lines are the ground (negative of the battery). The low and high beams as well as the relays are permanently connected to the ground.





When you switch the lights on low beam then battery positive will go to the coil of the low beam relay via the yellow wire that is marked “ to existing wiring harness”. This yellow wire will bring positive from the low/high beam switch. As there is a permanent negative on the relay’s coil this incoming positive will activate the coil and the contact of the relay will close. Positive will then go from the battery, via the fuse, through the low beam relay’s contact to the low beam filaments of the left and right lights (yellow wires) These filaments have perm negative (ground) and will light up.The high beam filaments will not come on because there is no positive to them.





When you now switch from low to high beam the positive on the yellow wire will be switched to the green wire that is marked “ to existing wire harness.) This switching will happen in the low/high beam switch. The high beam relay will then get positive and the contact will close and it will send positive to the high beam filaments (green lines)





This circuit is for a four light setup, two lights have low and high beams and two of the lights have only high beam. If the lights are on low then only two lights will come on and when on high then all four lights will come on.





The problem is that this circuit assumes that the positive gets switched by the low/high beam switch. In some vehicles the negative gets switched and the whole circuit will have to be modified a bit. The other problem is the one fuse system as already mentioned.





With after market circuits like this it is always very difficult to explain everything because the existing wiring on different vehicles are not the same. The main differences are the different ways that the on/off and low/high beam switches work.





Hope it helps.Can someone explain how this headlight wiring diagram works?
On the right where there is a striped arrow looking thing, thats the ground. The squigly thing after that is a fuse.The two boxes are switches pretty much, and the lines are wires. It's pretty confusing, and I see how your having trouble understanding it.