I am trying to find a good 12v source for my fan using a fuse tap. I ruled out all the constant power sourced fuses. my problem is that when I tap into something like the cig lighter or engine fuse and the fan comes on it drops voltage down to 10v and creeps back up to about 11v (per my aftermarket gauge). Is this normal or will that cause too much of a drain on my electrical system? I have seen other older vehicles wired up relatively the same way and they do not experience the drop like I do. It does not do the drop when I tap into one of the constant power sources. Does the amperage matter? ( I have 10 and 12 amp fuses to choose from). Thanks guys!

 

You are referring to an electric cooling fan for the engine right? If that's the case, use the battery as your power source rather than sharing the load with a circuit not designed to handle the current required of a fan that draws a lot of current (~30amps). If you'd like to have control of the fan manually, just wire up a relay using a switch inside the cab.

Here's how you'll wire it:

 

Thanks for the reply! Correct me if im wrong but if i wire up like that wouldnt it be running off a constant supply and continue to run with the key off?

 

Yes it would. You can control it with a toggle switch or tie in the control wire to something in your fuse panel. You should ALWAYS use a relay when wiring an electrical fan.

 

nevermind i answered my own question. the switch running to 86 can be from the radiator probe switch.

 

The schematic I posted has a switch.. I didn't write it "Switch" in there, but that could be a toggle or a factory switch.

 

cool thanks guys, i was wiring it up all wrong, i need to order a relay and wire it up the right way.

 

You can find a good SPDT relay at AutoZone or any other auto parts store. Good luck! Hope we helped ya out!

 

yes you guys did thanks a lot! i dont know what i would do without the forum!

 

When in doubt. Always run a relay like posted above. Its the best way to go with any aftermarket electrical item (off road lights especially). Have fun and be safe!

 

would a little fuse block with say a 30 amp fuse in it work in place of a relay??

 

Not in place of the relay, but certainly before it. Preferably within a few inches of the battery.

 

so would a relay come with an electric fan when i buy it? or would i have to get one? if i'd have to get one what would i have to buy?

 

I got my fan out of a newer model junk nissan truck. its just a motor with wires so no relay.