I also made my own, but have a relay for each filament. (4 relays)
If one relay feeds both low beams and one feeds both hi beams, then the loss of one relay takes out both lights.
Didn’t like that idea much.
Also all headlights are now 10 ga. wire including the grounds.
Relays are probably 40A, minimum 30A, so the relays should last for decades. Should use circuit breakers on at least the low beams as a blown fuse can leave you without. A circuit breaker will reset and lights come on again.
Ran into the circuit breaker kicking out on a Vauxhaul after I installed halogen headlights. Of course they went out only after getting on a dark country road going home. I fixed that with one relay for left hi beam and one for right hi beam with a 30A fuse for each side. The original wire to the high beam can be removed from the socket and installed on the relay control circuit, 85 or 86. Then run a 10 ga wire from the 87 to the hi beam socket position.
Electric fans draw a lot of current so a 40A relay and fuse should be used with 10ga wires from power to the fuse, from fuse to relay and then to the fan. The control circuit can be 16ga as it requires very little current. A 200° temperature switch will turn it on and off. Other temperatures are available, but should be 10° to 15° warmer than the thermostat.
