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Got this fuse block off amazon less than a year ago, says it’s rated for 100amps, 30amp per fuse. Fans are Derale shroud kit with dual Spal 12” pullers. Fuse block has 8 gauge OFC welded cable for power and ground. Wiring to the fans are 12gauge and relays are 80 amp each with wiring in the 12 gauge range. This is a 3 relay setup to create a dual speed controller for dual fans. I have run the car maybe 10times and I was just looking the car over and noticed the fuse block is melted! Looks like it melted around both 30amp fuses and the main ground connection. I tested both fans with a high accuracy amp meter/watt meter and the fans pulled 31+ amps start up spike and quickly dropped to 15ish amps running. Wired together I get both fans on a 1/2 speed soft start (fan 1 activation) and then 2 fans high speed with the fan 2 is activated.
What do do you guys think? Think it was the cheap $20 fuse block? I just ordered a real blue sea fuse block (same style) and it should be here tmrw. I run a blue sea 12 circuit fuse panel and it has been great. Maybe the $15 cheaper amazon one wasn’t up to the task!
It’s melted because your ground is bad. Either the ground wire is to small to support the load or your grounding location is bad. Also if your ground wire is longer than 12” that can also be an issue. The longer the run the thicker the wire needs to be. Increase ground wire size and use a multimeter and measure the actual current draw and amps used. For 100 amp current draw I would recommend 2 gauge wire 4 gauge maybe if it’s pure copper OFC. Are your fans independently grounded or run to the relay center. Maybe consider grounding the fans separately to your frame or radiator support.
Welcome to every electric fan installation, like, ever
I still remember my first set of high perf Flex-a-lites. Dual radiator fans that came with a thermostat/relay. The relay of course melted after a few weeks. The relay that it came with melted...
It took a couple tries but I get it right now. For electric fans, use 2x high quality 40-60amp relays for one big fan, or 3x 40-60amp relays for 2x smaller fans. overkill...
For the fuses though this is important. I use only OEM quality fuses from junkyard vehicles. For example
This one is my favorite. Its from some kind of SAAB. You wouldn't believe how hard it is to find fuses packaged with high amp relays in tight little water proof boxes.
I love that one because it has a huge 60-80amp fuse slot which ties to a 60/80amp factory relay. Perfect for fuel pump IMO.
Next, I find these in some Toyota I think,
Again look for small water proof box with relay/fuse combos. The fuses will sort of tell you what kind of current they support. If you see a bunch of 10 and 15 amp fuses it probably only has wire size large enough for that fuse so be careful.
The point here though is when it comes to electrical fuses/relays don't @(*#()@#* around. get some of this OEM quality stuff from vehicles that you know will last forever basically... Don't EVER buy some kind of aftermarket panel for $12 from the internet to do these duties
If you look in the bottom right hand corner of the picture you can also see some more factory fuses in a factory fuse 'holder' It just makes sense to trust OEM equipment wherever possible. If you want to try some kind of fancy panel/fuse setup downstream I suppose it would be ok as long as the backbone fuses that come beforehand are OEM quality.
Only thing in my opinion that would cause that is a loose connection.... Your wiring looks good so it's got to be in the block
Thats what I'm thinking. I got a refund on the box and got a better/nicer and more expensive blue sea panel. I just installed it yesterday and went through testing it.
It’s melted because your ground is bad. Either the ground wire is to small to support the load or your grounding location is bad. Also if your ground wire is longer than 12” that can also be an issue. The longer the run the thicker the wire needs to be. Increase ground wire size and use a multimeter and measure the actual current draw and amps used. For 100 amp current draw I would recommend 2 gauge wire 4 gauge maybe if it’s pure copper OFC. Are your fans independently grounded or run to the relay center. Maybe consider grounding the fans separately to your frame or radiator support.
Grounding is same as feed, both are 8 gauge OFC wire and the ground is 12" or less. Each fan was tested with a high precision Amp meter which you saw in the original pic, it gives me Amps/voltage and watts. Each fan startup spikes 30+ amps but settles into high 14-16amps running at full speed. I replaced the fuse block yesterday and decided to test them as wired vs separate. This is setup like a GM 2 speed (3 relay) harness. Basically the fans are run in series which cuts the voltage down (both fans start on like half power so the initial spike is MUCH less and the speed is as well) before high speed is engage which the spike is lower bc the fans are already running. Think of it as a 2 speed soft start setup. I have attached the diagram, so basically only 1 fan is grounded. Stock fan wiring is around 14-16 gauge so I stepped it up to 12 gauge for and connections/length increases which are short (less than 2 ft total). The fan relay/control center is literally right next to the fans/rad.
So I shot a video of my fans watching the amp meter and they show a soft spike of 20 something amps but settle down to 8-9amps running low speed at 115w. High speed activated both fans amps spike to 38amps but settle down to 28amps and 330w. My charger couldn't keep up on 15amp setting (next was 50amps lol) so battery voltage dropped quickly during the testing so I could never maintain 14v. I tested a few fuses, I stepped down to 25amp fuses and ran the fans and no issues, ran 20amp fuses and had no issues but decided on the 25amp as when I activated only the high speed without the low speed the fan 1 fuse popped at 20amps and it did not at 25amps. So when you really break it down with the data I'm at 28amps TOTAL running both fans on HIGH, which 8 gauge is more than enough to handle. I don't plan on running anything else to this panel and 8gauge at 4-7ft which i'm at about 6ft is good for 50-85amps which I'm not even close to. I realize that putting both fuses next to each other should have been fine but could be part of the problem with the cheaper fuse block. I spread everything apart on the new setup and made sure everything was tight. Fan fuses now have a blank spot between them and I moved relay activation 12v fuse to the other side (low amp powering of relays for ground triggers).
Thats what I'm thinking. I got a refund on the box and got a better/nicer and more expensive blue sea panel. I just installed it yesterday and went through testing it.
We use the Blue Sea on our emergency vehicles, great quality and have never had an issue.
We use the Blue Sea on our emergency vehicles, great quality and have never had an issue.
I agree, I have there 12 circuit panel as my main panel and it works great! I tried to save a few bucks and figured since it was rated for 100amps and I was only using it for the fans (30amp running for both) I figured I was safe at 1/3 the power rating. But I guess since its only at two fuse ports I overloaded it. Time will tell with the blue sea panel.
Thats what I'm thinking. I got a refund on the box and got a better/nicer and more expensive blue sea panel. I just installed it yesterday and went through testing it.
Good job... hope it works out for ya.... Never use cheap anything when it comes to electricity !!!!!
06-30-2019, 09:50 PM
Melted fuse block for fans but fuses didn’t pop? 
