bad_ta_05

ok, i just got a new 10 inch cooling fan to put in front of my radiator. i want to run it to an led lighted switch and i have a mccord exhaust cutout on its way and i also want to run that to a led lighted switch. well i went to autozone today and they have these add a fuse kits so i got one but the max amount is only 10 amps u can run through it. is that enough for my fan? i also have a painless wiring harness on its way for the fan that has a relay adn all the wiring and stuff i am just worried about running power to it and i figured best way would be through teh fuse box. and this add a fuse kit is really simple but if i need more i will go get one of those small fuse blocks and run it to that. but do u thikn the fan will need more than a 10 amp fuse or the cutout? also how do i hook up an led switch? there is 3 pugs on it. power and ground and another one. so run strait power from the fuse block to one, then out the other to the relay adn the fan and then the last one to ground? this is my first time ever wiring up anything other than a radio. sorry for all the questions i just dont wanna blow up anything :P. thanks for any info!

dyeager535

OK the LED/cutout stuff I'm not going to touch.

With the fan, to make it work only when the ignition is on, you need the "switch" wire from the fuse panel, but from a port that is hot only in run. It takes very little juice to switch the relay, thats why they are used.

One small wire to the relay switching side from the fuse panel, and the other small wire will go to the temp switch or however the painless setup works. Switch grounds at a certain temp, and that switches the relay.

Two large wires to the relay. One straight from the batt. + to the relay, and the other goes to the + on the fan motor. Ground the - fan motor wire to the body.

Not sure on your fuse panel, but most GM stuff in the 80's-up uses fuse panels with empty "accesory" ports. Get the right connector from a junk car, solder the relay and connector wires, and you can save yourself future hassles, as it will never come loose.

I'd suspect 10 amps is too low. I saw somewhere that the stock fan(s) draw somewhere around 20A at startup, and run at about 8. Definitely don't want to run the ragged edge, you WILL end up with at best melted components, at worst a fire.

bad_ta_05

i think i figured it all out i will just tap into my fuse block power, (only on when key is on), then i will run power to another 4 circuit fuse panel from auto zone, 6 bucks), then run power to my led switch, ground the switch, then power out through the relay and strait to the fan. will do the same with the cutout and then mount the switches in my ashtray compartment. will this work? i have a fuse and a relay for the fan and a fuse for the cutout and the fuse panel will only be on when the ignition is on. so it should work good shouldnt it? will my switch be placed in teh right spot? thanks alot for any help!!

dyeager535

Just need to give/get a few clarifications.

You do understand that not all of the fuse panel is hot only in run, correct? If so, great, just making sure.

You are not talking about running the large wires (the ones that need batt voltage to the relay) from the fuse panel you are thinking of buying, correct?

Doesn't the painless kit come with a temp switch? I know they make the "probe" style that fits into the radiator. Unless I was drag racing or using a truck in deep water, I can't think of a reason to not leave fan control up to a temp switch. Perhaps an override if you were really concerned, but an adjustable temp switch would be 10 times more convenient.

My understanding of your idea:

Auxillary fuse panel fed off of the stock fuse panel. 12V for the switching side of the relay off of this new panel. You would switch ground to the relay with your LED switch. That should work fine.

I personally would do away with the LED fan switch idea though, and either get a stock temp switch (the 80's GN switches come on at like 200* or something, probably can find that in a search on this board) or as I mentioned, a variable if you want it coming on at lower than stock temperatures, although that is just a band-aid and does nothing for actual cooling effect.

With a stock fan switch you can just run ONE wire out of your passenger compartment, as the switch handles the ground. In that case you wouldn't even need the extra fuse panel, as long as there are enough empty accessory terminals on your fuse panel. If your panel is like the 80's trucks (plastic blade fuses) you can "stack" the connectors, so even one terminal can feed 2 or 3 seperate wires.

Have to double check though...the relay 12V ignition feeds are fused from the factory, and at least on some of the later fuse panels, some of the terminals are run through a fuse (no problem there, just use appropriate fuse) and some of the terminals are run off of a 30A circuit breaker, which probably won't be a problem, but COULD be. (just because it will reset if there is a fault, and 30A may be too much, although I doubt it will matter if it shorts to ground)

bad_ta_05

im running the fan to a switch because i dont need it very often. just sitting in traffic or at really slow speeds and the painless kit i got was only 20 bucks and just has all the wiring i need and a relay, no temp switch. also winters here are really really cold and i dont need it in the winter. indiana weather is the weirdest! another problem with the temp switch is i have no place to put it. i swapped heads so i had to move my actual guage temp sensor to front of the intake manifold. so i really dont have anywhere to put it and im way over budget as it is so im trying to keep costs down as much as possible. as for the fuse panel. there is an orange wire that goes to a few things, i was going to tap into that because its only hot when ignition is on, correct? i will check it to just make sure with a test light. all i have to do is run a 12 guage wire from the panel, to the switch adn relay adn then to teh fan adn then i can ground the fan on the body someplace correct? should i put the switch before or after the relay, thats the only thing im not sure about. thanks for ur help dyeager!

dyeager535

OK first off, I will NEVER condone tapping into wires that don't need to be. If you've got accessory terminals on the fuse block, use them. I can't stand hacked wiring when there is no reason for it. No offense, just trying to help out...splicing into wires, especially as important as things in the fuse panel (like any wiring exists that isn't important) will do nothing but cause you future problems. (ask anyone that has dealt with hacked wiring) You introduce corrosion, possibility of breakage, poor connections, etc. Just get some of the terminals out of a wrecking yard and go that route. Believe me, it not only works better, it's cleaner and easier to deal with, especially if you ever want to remove it. You just unplug it.

Sorry for the rant, wiring and fuel are two of the things I don't screw with. I don't like troubleshooting electrical problems, so I do it "right" (my way lol) the first time. However, my way is the way GM did it, so I'm hopefully backed up by billions in research

The purpose of the relay is to keep the wires that are carrying the current as short as possible. So no, you do NOT want to run them from the passenger compartment. You have many options, one of the easiest would be a ring terminal (you can buy big ones at radio shack I think) that fits under your battery cable. You would want to mount the relay up near the fans/battery, as close as possible. The longer you run the wire carrying the current, the more resistance, and the more heat. Heat is bad.

Thus, the purpose of the relay is to act as a remote switch for the short wires doing all the work. Since the relay part that switches needs very little current, you can run small gauge wiring long distances, (IE from fuse panel, and back to the engine compartment to your switch) and not have to worry about resistance. This way, you shorten the "path" of the wires that do all the actual work, if you will.

I'm not sure that you understand how the relay works, so here you go..I'm no electrician, so I may have terms wrong, but this should be a "backyard mechanic" description.

The relay is two parts. One "side" is a simple switch. (2 wires typically) The other "side" of the relay is simply the contacts for the switch...thus, the two large wires that carry the current are isolated from each other, until the small wires "tell" the relay that the two large wires need to be connected. (in our cases, usually when the 12V ignition wire is switched to ground) When the 12V ignition wire is grounded, the two large wires are then "connected" and your fan gets power.

I think maybe you aren't clear about the ignition 12V....with a relay, you don't need to worry about the fan itself being hooked up to ignition 12V. Unless the side of the relay that sees 12V ignition is grounded, AND has power, the fan simply cannot run, so you hook the one side of the relay up to the battery directly...again the shorter wire advantage. With the key off, that 12V ignition wire gets no voltage, thus it can't switch.

I guess a failure of the relay could cause the fan to run with the ignition off, but it's obviously fairly rare, I've never heard of it happening.

Your switch will do nothing except ground the side of the relay that does the switching. I don't know that any switches as small as would be used in a car would be able to handle 20+ amps, so i fyou tried to run your fan wiring through that switch, you would shortly burn it out.

I'll give you insight as to how I wired mine up, hopefully you will get a better picture. I've got dual fans, but I'll deal with the secondary fan, since it is almost identical to your intended setup.

There is one small wire coming from the fuse panel, 20A fused 12V ignition. This wire runs to the relay. The OTHER small wire (this is the switch side of the relay) goes straight to a temp switch in the cylinder head. When it hits X degrees, the circuit is grounded. That makes the relay switch. (the temp switches cost about $10 at Napa FWIW)

The other "side" of the relay, is the switched large wires. There is a ring terminal on the battery, that has a the large gauge wire running to the relay. The other large wire coming out of the relay goes directly to the fan +. (well, mine has weatherpack connectors so I can pull the fans easily if need be) The ground wire for the fan, has another ring terminal on it, which is bolted to the core support.

In operation, the fan can NOT run until you turn the ignition on. Cold engine, turn ignition on, that small wire "sees" 12V. Since the engine is cold, the switch in the head does not switch to ground, and the large wires to the fan from the battery are not "connected". As the engine hits the temp switch on rating, (say 220*) the switch grounds. This means that the 12V ignition is now going to ground. The relay sees this, and allows the two large wires to be connected, and the fan comes on.

Hope that helps a bit. Not trying to be condescending or anything, just easier to write it all up in one post, in case it WILL help you understand.