Ok, I did a little testing today and these fans blow 30 amp mini fuses like nobody's business.

I wired each fan on its own dedicated circuit. 10 gauge wire from the battery to a 35 amp ISO 280 mini relay (2.8mm terminals), then stock 12 gauge wire from relay to a 30 amp mini fuse (2.8mm terminals) and then the stock 12 gauge wire to the fan using the stock connector.

First time I hit the switch I had 20 amp fuses in there just to see what happened. Bam, popped the fuses instantly. I then switched to the aforementioned 30 amp fuses, clicked the switch on and the fans ran for about 4 seconds and it popped again.

This seems a little weird to me that the stock 40 amp fuses would hold up forever yet blow a 30 amp fuse instantly. I'm wondering if the small 2.8mm terminals on the ISO 280mini relay and the mini fuses has something to do with this. It did not hurt the relays at all.

This has me scared so I think I'm gonna stay way from the 2.8mm stuff.

Any input???

 

Excessive current blows fuses...if you're running too thick of a wire, current will increase and will require a bigger fuse. What size wiring does the factory run?

 

Big wires have less resistance, not necessarily more current. If you are blowing fuses that easily you wired it up wrong.

 

Bigger wire does not increase current draw as it decreases resistance.

I re-checked the wiring and it is correct. Used a test light at each terminal, relay does not pass current until the manual switch is closed.

The 2.8mm (metri-pack 280) terminals are only rated to 30 amps. I'm wondering if the small contact patch of these terminals creates too much resistance in a high current draw situation (e-fans) causing the amp draw to actually increase. Would that make sense?

Metri-pack 280 terminals allow for nice packaging of fused/relay circuits but there is a reason GM doesn't use them on the e-fan side of things. I think it was posted above, but GM uses Metri-pack 630 terminals on the fans which is alot more robust, and those engineers are alot smarter than me. I was just hoping to get lucky.

I'm gonna do another test tomorrow using std. 1/4" terminaled relays and fuses and see if the 30 amp fuse will hold up. If so, that would answer my question above and some be some nice tech info for others. If it does pop at 30, I'll try a 40 and see what happens. If it pops that, your right, I do have other issues.

Stay tuned for test results.

 

Go take a look at Ohm's law, as resistance goes down, current goes up, this is elementary stuff. Take two lengths of wire, with the same power source (say 12v), the same load (try an 1157 bulb), and one with 12ga wire and one with 10ga wire, and I guarantee you that the circuit with the 10ga wire will have higher current when checked with an ammeter. I learned this in the GM SET course over 20 years ago, it's one of the first things that they teach you when learning electrical diagnosis. Current goes up as resistance goes down...simple as that.

Folks who don't understand Ohm's law should put the wiring down and step away before they start a fire...

 

I just wanted to add something that may help a few folks, as I'm honestly stunned that guys wouldn't understand the concept of current increasing as resistance decreases. As mentioned, I was taught this a long time ago by GM, then re-taught this by Toyota, and I had the pleasure to teach it myself as a training specialist for Toyota Motor Sales, U.S.A.

Get a plastic bucket of water, call this your battery. Look at the ground...this is your ground lol. Now drill a 1/8" hole in the bottom of the bucket and observe how fast the water runs out. This rate of water departure can be considered your current. Increase the size of the hole, to say 3/8" or 1/2"...this is the same concept as increasing the size of wire...observe how much faster the water runs out, this simulates increasing current. Also, as you add more branches to a parallel circuit, current will increase. You can observe this by drilling more holes in the bucket, which simulates adding more branches.

As you increase current, and if your wiring, switches, relays, and loads are all capable of handling the extra current, you will require a bigger fuse, as you will easily blow the smaller fuse that was intended for the circuit with more resistance, which will ALWAYS equal less resistance.

Here's a good website for those of you who are willing to learn and want to tackle your own electrical projects: http://www.the12volt.com/

For those of you who aren't open minded and think you know it all already, good luck, and keep a fire extinguisher handy...I can't begin to tell you how many vehicles I have seen towed into my shop because of DIY electrical installs that have gone bad.

BlackBear and Nelson make really nice efan harnesses for those of you who don't know and don't believe the age old concepts outlined by Ohm's Law...it's quite simple once you have the correct knowledge.

I don't mean to be harsh, I'm just flabbergasted that guys would post that decreasing resistance will have no effect on current flow, those statements are 100% wrong, and the idea of that train of thought is downright scary to someone who has actually seen cars on fire before.

Hopefully this post will educate some folks and help them to realize that not everything is cut and dry...when doing DIY electrical installs, you should have a deep understanding of Ohm's Law, a pen and paper, and a calculator, if you're going deeper than just wiring in a stereo with a plug and play harness, or just some air horns or fog lights.

 

how many amps do these 05+ truck fans pull at "start up ?" vs running amps ??

 

What you said is certainly true, but it is a bit deceiving to simply state that bigger wires will draw more current. In your example, if I use some 000 gauge wire to power a light bulb it would draw hundreds of amps of current...

The majority of resistance of any circuit comes from what you are actually powering; the filament in a light bulb, or the windings in a DC motor (our efans). The resistance of the power wires are a SMALL part of the total series resistance of the circuit. The problem arises when the current dictated by the motors is greater than the dissipation capacity of the wires, that is why undersized wires melt and you have fires. Power goes up with the square of the current times the resistance, so if I double the current, its 4 times as much power. To make it even more fun, the resistance of wire is not constant but increases as the power goes up (from heat). Again you are current according to ohms law current goes up as resistance goes down, but I reiterate that the resistance of the wires are very small compared to the fan motors and the addition of larger wires will not cause an appreciable increase in current load.

 

With the load being constant in this case (same fan motors no matter what size wire you're using), if you increase the wiring to these motors you will have more current in the circuit, possibly requiring a bigger fuse, depending on what size fuse you're already using. If one is increasing the wire size, they might want to consider what size fuse that they're using. Some folks have a tendency to use something monstrous like 0 gauge for instance, thinking that they're doing themselves a favor. An increase in wire size like that will definitely cause an increase in current which will not only blow fuses, but may actually smoke the fan motors. An increase from 12ga to 10ga will allow for a current increase that can be read on an ammeter, this is a fact, and something that I've seen first hand many times. To say that increasing wire size, which decreases resistance, has no affect on current is completely incorrect and misleading to those who may try their hand at building their own harnesses and decide that "hey, if 10 is better, why not try 8, or 6, or 4!". I just don't want to see our do-it-yourselfers entering into a potentially dangerous situation because they have received information that they think is safe and sound

 

I dont want to see anyone burn their project down either, but saying you have to be extra super mega careful not to use too big of a wire is a bit far fetched. Im not arguing with you that it will cause an increase in current; the argument is with the scale. If DOUBLE the size of the wires, but the total circuit resistance from the wires is only 0.1% your total change in current is 0.05%. Say its a 10amp draw, that means the new circuit is 10.05amps. I would much rather overestimate my wire size, then risk overloading a wire and melting it through because I was worried about an insignificant increase in current draw.