hot, smoking headlight switch

[simplyconnected]

I'm not sure I understand because your alternator wire should go to your battery (or starter sol +12 post). It is already constant power.

As far as relay draw, the relay coil is only on with the headlight switch (in this case). Contacts don't pass power until the headlight switch is pulled.

Overcurrent protection is there for the wires or contacts, which ever has the lowest rating. Ex: if your wire is small like #18, it safely passes 10 amps continuously. So a short on this wire should blow a 10-amp fuse without damaging the wire. Hopefully, the relay contacts are rated for 10 amps as well. - Dave

[Guest]

Very true Dave, silly question.
All good, I'm going to use 20 amp relays with 10-15 amp fuses which from what I've gathered should be more than enough.
Slow process unwrapping all the neatly hidden wiring to find 2 wires, enough to pull your hair out, especially when it took hours to rerun the first time. Oh well.
Cheers Chris.

[simplyconnected]

Chris, there is no silly question but there are unclear answers that beg further explanation. If I'm not clear again, I invite more questions.

Your proposal of using 15 amp fuses sounds ok to me. Think of auto power in terms of watts (volts times amps). In household wiring, 15-amps produces over 1,000 watts but in automotive circuits, 15 amps produces only 180 watts (less than two 100 watt light bulbs). The situation was even worse when we used six volts because 6volts X 15amps = 90 watts. We are forced to use high amperages and large wires to get serious electrical work done in a car. - Dave

[Guest]

Well I have thrown a few at you over time I guess.
What I am wondering now is would it be worth going down the same path with the horn since I have the loom apart.
I did install a large fuse panel a while back with 12v running to it and I've still got plenty of space.
Thanks Chris.

[simplyconnected]

Yes Chris, but the horn is wired slightly differently. One coil wire is connected directly to power while the other coil wire connects to the horn ring. Once grounded at the horn ring, the relay energizes, closing the contacts and making a completed path with the horns.

So, the OEM horn relay is no different from any other relay and it has large contacts. In my book, these relays are overpriced because comparable relays cost only a few bucks. - Dave