Black Z-24

Ok, long story short, my car sucks and I have a switch right now to turn on/off the cooling fan until I fix it.

I have the power wire running to the switch (from the alternator 12V source), then another wire from the swtich to a fuse, then to the positive side of the fan. When I turn the fan on, the wiring right next to the switch gets unbelievably hot, yet the wires further away are touchable.

I want to know how I can prevent this? I have a 25 fuse with a 12V rocker switch and 12 gauge wire. Do I need a bigger fuse, thicker wire, better switch?

Fabrik8

Use a relay. That's way too much current to put through a switch. Use the switch to toggle the relay, and just run power from the battery, through the relay, and to the fan. Then run a wire to the switch to trigger the relay.

Black Z-24

I need a little more help

I got a relay, and have no idea how it is supposed to be wired. I understand the gists of power and ground, but this shit doesnt make sense. Heres a pic if somebody could draw how its supposed to work.

Fabrik8

Ok, your picture doesn't help, so here's a description. You'll have to get the relay pinout on your own. Here is the breakdown of what is happening here. A relay is switched by applying power to the coil, and there are two ways of doing that. For your purposes, (turning the relay ON when you flip the switch) you can either put power directly to one side of the coil, and have the switch wired to ground (switch completes circuit to ground) or attach one side of the relay coil directly to ground and have the switch supply power to the coil. Again, either way will work. Now, for the high power stuff. Most (many?) automotive relays have two connections, a normally closed and a normally open. You will want to turn the relay on with the switch when the car is on, so you will need the normally open. This way the relay is off until you turn it on. Simple enough.
To wire the fan up, you can either put the relay inline with the power or the ground, and then hook the other up to the other choice. It doesn't really matter as long as the power wire goes through a fuse immediatly after it comes from the battery or wherever. I suggest putting power through the relay, and connecting the ground of the fan directly to ground. This is a little bit better for safety because then the fan has no power anywhere near it if the relay is off.
Now that i've bored and confused you, give it a try..

Black Z-24

Ok, I think I may have it, but I still have questions. I am gonna try to make this as uncomplicated-sounding as I possibly can. Bear with me.

Relay was your choice to keep the power to a minimum around the switch, so by this I assume using the "attach one side of the relay coil directly to ground and have the switch supply power to the coil" method would not work in my favor, because power would lead directly to the switch, then to the input on the relay, which would heat the switch up. As of now, I don't have a fuse between the switch and the power source. I did before and the fuse melted.

So, I am going to use the other choice, "you can either put power directly to one side of the coil, and have the switch wired to ground (switch completes circuit to ground)".
This means I am going to run my power wire through a fuse (what size?) to the coil, then from the coil to the switch...>>>then from the switch to the ground on the coil? (Confused here).
Then where does the positive and negative fan terminals lead to.

Thanks for helping, this shit sucks.

Black Z-24

Ok, I figured it out. It works like a dream now. Thanks for the help.

MerF

Just curious, but was it because you had it hooked up to the alternator source? Way to much fucking current for a little switch/wires, wasn't it?

Black Z-24

Yeah it was. I couldn't get it on the battery because of how short the screws are, so I routed it to the alternator. Needless to say, now, it works exactly how I want it.

How'd you guess the alternator?

MerF

Similar problem in another thread actually...that guy melted half of his wiring harness though.