802maro

i swapped a carb 350 into my car. the passenger side fan ran constantly, and the driver side fan never turned on. so i decided id wire them into one switch. the switch has an LED light on it. both power wires are hooked into a female connector which is then connected into a single 10g wire that goes to the switch. i then used a 10g wire with a 30a fuse from the battery, then to the switch. i then grounded the switch. the fans are both grounded to the body.

when all was done the fans turned on perfect and ran great. started the car and headed to town. got up around 200degrees and decided id turn the fans on... well no led light made me worry, so i pulled over and found the fuse blown. had to wait for it to cool down then drove it home. now the led light doesnt come on but with a new fuse it still turns the fans on.

now i have realized that with the car running, when i switch the fans on... it seems to lug the engine like crazy! why would they be drawing soooo much power? it almost shuts the car right down. i cnt seem to figure out why im blowing the 30a fuse either. it seems to be random.

sofakingdom

iTrader: (1)

That right there is why.

The switch won't last long either, or the wires; esp not if the fuse doesn't blow for some reason.

Looks like you have it wired such that when you turn on the switch, all that happens is, you short the battery (and alt) out. Keeping in mind of course that the alt doesn't just miracle power up out of nowhere, but rather requires engine power to drive it to generate the electricity, when you put that MASSIVE load on it by shorting it out, it suddenly goes from taking like .2 HP to turn it, to about 5 or 10; which of course, loads the motor down SEVERELY.

To run your fans, you NEED a relay. There's NO WAY the arrangement you have will work for long or be reliable, even if you wire it "correctly" to the extent that it can be.

Instead, get a relay. Connect your wire from batt to one contact, and the wire to the fans to the other contact. (if the relay has multiple contacts, select a pair that is not connected when the relay is at rest, but gets connected when it's energized) Connect one side of the relay coil to ignition (hot only in Run is preferable if you can find it) and the other side of the coil to one side of the switch. Ground the other side of the switch. Now, when you flip the switch, a TINY amount of current will flow through it and energize the relay, and the YUUUUUUUUUJJJJJJJE fan motor current will flow through the relay contacts.

The LED in the switch won't work. But it's basically pointless anyway, tells you nothing of value, so NBD.

802maro

do you know of a relay i could use? i know nothing about them, how they work, and or function. i looked at some of the relays on my cummins and they have 4 male prongs i could run connectors to easily. i just would have no idea which prong to run any my wires to. i have no problem with the led not working.

sofakingdom

iTrader: (1)

Relay = electrically operated switch; a motor that flips a switch, if you will

It's a small, simple, versatile device that allows a very small low-power signal to control a very large high-power load.

It consists of a coil (electromagnet) which, when electricity is applied to it, moves another iron piece with contacts mounted on it, such that when the iron moves (as a result of the magnetic field being applied), the contacts change state. (either make, which is what you need, or break; or even, do both at the same time)

Not sure how anyone of normal intelligence (can type on a keyboard) can possibly not understand this. It just about doesn't get much simpler.

Put out of your head all that stuff about "it's hard", "I don't understand electricity", "prongs", and all that. Get the basic concept mastered. Maybe look it up on HowStuffWorks.com or Wikipedia or something complex like that. You'll laugh at yourself for having convinced yourself somehow that something so ridiculously simple, that the human race mastered centuries ago, was beyond you, and maybe even develop a thirst for further learning.

802maro

my question is how do i go about getting the "right" relay for this application. by your first post, it seems ill be looking for a relay with 4 terminals. like the ones on my truck. but without being able to see into the relay to know which wire to hook to which terminal, how do i know what im doing without destroying the relay? thats what im not understanding

sofakingdom

iTrader: (1)

You can hook up your ohmmeter to the contacts. If there's no continuity with nothing else hooked up, but then there IS continuity when you apply 12V to the coil, and the contacts are rated for at least 30A, then it's what you need.

Did you read the Wikipedia article, especially this section right here https://en.wikipedia.org/wiki/Relay#pole_and_throw down toward the bottom right above "Applications" where it gives the DIN standard automotive terminal numbers?

You can get a suitable one at AZ or about anywhere else that sells automotive relays. You could even go to the junkyard and get one off of a car; a cooling fan relay, or a blower high-speed relay, would be about perfect:that way you could even snag the matching connector, with nice colored wires, and then it would be obvious how to hook it up.

I can't stress the point enough, this just isn't that hard. I'm REALLY REALLY DUMB, and even I can manage it. Surely you can. Put aside all your "I can't" and call upon your "I will" instead. You can DO THIS.

skinny z

I was going to suggest this thread:

https://www.thirdgen.org/forums/cool...me-figure.html

but I think the above post has all the info you need.

802maro

So I went and picked up a relay for like 6 bucks. It even comes with a wiring diagram and exactly which wires to put where on the back of the package! Lucky me. Im just wondering, this relay os rated for 40 amps... should I still be running that 30 amp fuse on the 12v supply wire before the relay? After the relay? Or just get rid of it. Thanks for your help

skinny z

It's not that difficult is it? I like it when a plan comes together.
Keep the 30 amp supply fuse between the relay and battery (or wherever you're getting the power from). Best practices are to keep the fuse as close to the supply as possible. Be sure to have the correct size wire too. 30 amps needs a 10 gauge conductor. That applies to the ground wire from the fan as well.

802maro

okay i wire the relay in, wasnt very hard. i checked a couple youtube videos during the process because i wasnt exactly sure how to wire in the switch to the relay. i used this video and the exact circuit (i used the top diagram).


turned the fans on for the first time. they ran for about 3/4 of a second and blew the 30 amp fuse which is roughly 5 inches from the battery. all brand new 10g wire.

is the circuit i followed not what i should have done? i know you guys think this is so easy... but for me, wiring this stuff in is like trying to understand someone speaking a foreign language. im not understanding why im blowing fuses so often. what should these 2 fans be drawing for amps?

sofakingdom

iTrader: (1)

See, I told you you could do it!! Next thing you know, you'll be helping other people out with their electrical questions.

I'd use a fusible link, and put it right where it gets its battery from. As close to the source as possible. But a fuse would work too, it's just more likely to develop bad connections and go intermittent, than a fusible link. Like Skinny said, 10 ga. would be the size to use for the connections from batt to relay, relay to fan motor, and fan motor to ground. The wires concerning the coil can be quite small, 18 ga. would be more than plenty.

If it blew a 30A fuse, that means it's drawing more than 30A. Put in a 40 and see if it holds. Or, get rid of the fuse altogether, and use a fusible link instead. (rust color... they're color coded http://www.whiteproducts.com/fusible_link_wire.shtml)

skinny z

Or try this.
Forget the relay and switch altogether for now. Connect the fans directly to the battery using the 30 amp fuse. If that blows up, it's a pretty good indication that the fans are starting to seize. Try them one at a time first. Then together. Had that exact problem with the single fan in my Z.
If one or the other takes out the fuse, you've found you're problem. If they take out the fuse only when they're wired as a pair, then chances are the circuit is overloaded.

802maro

if it it blows the 40 amp fuse, then my relay is pointless becuase thats only rated for 40amps. luck hasnt been on my side, but hell ill try and see what happens.

sofakingdom

iTrader: (1)

Keep in mind, it probably draws a whole lot less while actually running, but for the first few seconds while coming up to speed, the draw can be REAL heavy. They actually make slow-blow fuses for motor and other similar high-inrush applications.

Or, if each motor draws 30A or something, you might need 2 fuses, 2 relays, and 2 sets of the high-power wiring, one for each motor. The coils can still be run both off of the one switch and its 18ga. wire. That's the benefit of using a relay.

(Yes I am an electrical/electronic engineer by trade)

802maro

i actually did that, to make sure that both fans were actually working properly. and neither fan blew the fuse. thats was when i first wired them in before i thought anything about a relay. i had them running together for quite a while without the relay, but i couldnt figure out why theyd blow the fuse randomly. maybe theyre flirting with 30 amps an sometimes they draw too much and blow it. idk. ill try the 40 amp tmro. thanks for the advice guys

skinny z

I believe this how the GM did it with their dual fans wasn't it? Separate controls though. One via the ECM, the other through the temp switch in the cylinder head.

Could very well be.

802maro

yea i read about a guy wiring in fans for a chevelle nd he used 2 fuses an 2 relays.
i read on this forum somewhere that people run them with just the fuse, but is frowned upon. and some run them with just a fuse and a relay. ill report tmro when i get the 40a.

skinny z

Please do. Not necessarily for my own enlightenment but for anyone following the thread. Yours is not an unusual situation for people making upgrades. And wiring seems to intimidate a lot of people.

802maro

i fit into the intimidated category. but i needed these fans to work to cool my engine. so far i have run the car 20 minutes turning the fans on and off several times. each time i turn them off i wait for them to completely stop rotating, wait a few seconds, then turn back on. havent had any blown fuse yet. that is a 40a fuse and 40 amp relay with 10g wire. which im pretty sure is only rated to 30 amps, as is my switch. so i should upgrade my switch for sure i feel like.

skinny z

Your switch only turns the relay off and on. It doesn't see the load of the fans as the power for them is passed through the other contacts of the relay. The switch should be OK. That's provided you've wired it correctly. The wire on the other hand, depending on the type of wire used may be fine for the increased current. Moving up to an 8 gauge wire gets complicated as the crimp-on terminals generally will only accommodate a maximum #10 wire. Keep an eye on it. If it becomes very warm after an extended period of time, you may want to make the move to a pair of relays (rather than moving up to larger wire). One switch can control both. The wiring is simple enough.