bare with my english guys, I need help how to use the relay for my aux fan speed auto adjustment.

basicaly, I just need the aux fan always at high speed, but when the headlight is triggered, the aux fan turns to low speed using the resistor block. using the negative line.

I need this functionality because my alternator cannot compensate 3 strong aircon aux fans our ride uses together with the headlight * night. ok lang sa araw yun 3 aux fan, but with the headlight at night, di na niya kaya ang load.

I already tested the resitor block, and it helped a lot lowering the load, upgrading the alternator is not on option. woould like to keep all 3 aux fan so I can maximize the cooling.

hope you could help me guys, thanks