3G - Too much power!

[BroncoMarc]

I just got my 3G conversion done and I fired it up for a test. I turned on most of my electronics (2 fans, fuel injection, headlights, arb valve) to give it a test. My original alternator had me down to 11 volts since I added the 2nd fan. All was going good for about a minute, then my main fuse blew. It didn't just blow.. The plastic was slightly melted.

All my wiring is custom since I've been buggyfied. I've got a main wire going from the battery to fusebox A. It goes thru a 30A fuse, then thru a big relay switched my by ignition switch. The relay powers up fusebox B which all the accessories are tied into.

It was the 30A fuse that blew. The 3G is the only change I've made since adding the 2nd fan a month ago. It ran fine for a week in Moab with the 2nd fan. I never blew that fuse with the original alternator.

Is 30A not big enough for 2 fans, fuel injection, minimal lights, cb, etc. ? Have I just been underpowering all my electronics with the original alternator and that's why it never blew?

 

[rob wilson]

Marc,

The maximum output from a 3G is several times the 30 amp fuse you blew. I'm guessing but the fans alone probably draw more than 30 amps. Time to up grade. I'd recommend a marine grade circuit breaker. Better than a fuse since it can be reset should it pop. Also a easy way to quickly isolate power to everything (except the starter) while doing maintenance. I used a 150 amp. It's installed between the battery and all of my loads. The output from the alternator goes directly to the battery.

Here is a link: http://www.delcity.net/delcity/servlet/catalog?parentid=193073&page=1

Use P/N 76620 if the link doesn't work

 

[DirtDonk]

When you had the old setup did you ever turn on all the other things at the same time and leave them on for awhile, like you did to test the new alt?
If so, then yeah, your fuse probably survived it because your old alt couldn't put out the power enough to heat things up.
I don't know what all you're running, but I'd agree with Rob that it's too small a fuse.
Even though your 3G might put out 130 or more amps, that's only going to go to the battery through the starter relay, if that's how you have your charging system hooke up.
All your main power to the fuses is going to see is whatever all of your accessories are capable of pulling through when they're all on. So figure out what that is and put a slightly larger fuse than needed. Especially if you're going to hook any more things up to it in the future. Such as more lights or something like that.
I bet you'll need more than that 30 amp'er in there.
By the way, how large is that main wire to your fuse boxes? And how big is your charging wire and what is it hooked to? Just curious.

Paul

 

[1977]

Waaaaaaait a minute. All I hear of here is to put in a bigger fuse. The only job a fuse does is protect wiring. You better make damn sure your wiring can handle more amperage than your fuse is rated for, or your gonna be in big trouble!!

 

[BroncoMarc]

For the charging system : My battery is in back. I've got a 1 gauge welding wire running up to near my passenger side shock tower. I've got Ryan's 3G harness with a 4 gauge wire going thru a Mega fuse. The 4 gauge wire, the 1 gauge wire and my winch wire are all tied togther.

To power things up I've got a 10 gauge wire running from the battery to the 30A fuse, to the relay to the 2nd fuse box.

Should I go bigger than 10 gauge?

 

[DirtDonk]

It's all about how many amps your accessories are drawing, and the length of the wire that has to carry it all. But normally from what I'm hearing yes, 10 ga is probably fine. Not overkill, but ok for general use. Unless you've got some high-draw accessories at the other end that is.
Then again, if your fans and stuff are running off of this, the 10 ga might only be ok if you're not running it too far. Probably fine, but...
Fans are still up front I presume? I haven't seen your buggy so don't know if it's remotely normal or some total exotic, but presumably your radiator is up front, so your main draws farthest away from the battery are your fans and your lights. Correct? Everything else is in the main "cab" so not all that far away from the battery?

You're right about not over-fusing a smaller wire 1977. Sounds like he's ok in this case though.
He can probably can get away with a 40 amp'er in this case. Maybe 50, but again, it depends on what you're running for total accessories Marc.

I guess before I give out recommendations I should know some more details though. High amp off-road lights perhaps? High-output replacement headlights? Big fans? Long wire runs?
Inquiring minds want to know.

Paul

 

[DirtDonk]

I just double-checked one of the readily available charts and it looks like the 10 ga wires are good for up to 50 amps if kept under 15' in length.
So your wire size choice, though not overwhelming in capacity, should be good for awhile as long as you don't exceed that length of wire or that amount of current for any length of time.
I do not know how much fudge-factor is put into those charts. It seems likely that they're a bit cautious in their estimates, but it's hard to say. The recommendations are probably for continuous duty, but it's always nice to add a little to recommendations when efficiency and safety, and not saving that last gram of weight is your biggest concern.

Paul

 

[SaddleUp]

Personally I would leave the 30 amp fuse in the wire alone. 2 fans, headlights, and EFI all being fed from one 10 guage wire just sounds like a recipe for disaster to me. The fans themself could potentially pull close to 30 amps each when they start. I would rewire all of the above so they each have their own fuse and feed wire running through relays instead. Or rather I should say that is how mine is wired (with the exception of the second fan which I removed some time ago and now use to feed the master switch on my dash for the in cab winch controls) I.E. Anything I run that draws high amps runs on a relay to keep from running high amps through the main harness.

 

[broncnaz]

You need to look up how many amps your fans draw looks like most fans draw 10-14 amps each with some drawing as low a 4amp while others drawing up to 25 amps a couple of the dual fan setups run a 40 amp relay. I'll piggyback on Saddleups post I would run a separate circuit just for the fans with its own fuse and wire straight to the battery Via a relay. You can run the relay for it with the switched power coming from your fuse block. Probably do the same for the lights. Everything else could be run off one circuit. look at how cars are wired up the electric fans are on a different circuit then the lights and stuff. lights themselves may draw close to 30 amps depending on what type your running. It all adds up to more wires but its way safer.

 

[BroncoMarc]

My tranny cooler fan is a 12" Hayden. Couldn't find specs. http://www.haydenauto.com/electricfans.htm

My pusher fan is a 16" Spal. The specs say it draws up to 8.5 amps. http://www.spal-usa.com/fans/automated/tech_sheets/0400-0401.pdf

I'm running stock headlights and LED tail lights. No off-road lights (yet, and I would put them on relays)

Both fans had already spun up and running for about 15 seconds when the fuse blew. I was also reving the engine to test for belt squeal.

I think my fix is going to be to put both fans on relays from the battery to lower the current going thru the fuse. I'll also bump up the 30A to 40 or 50 if I can find them (What's the largest blade fuse?)

It might be time to just totally redo my wiring. I've added on too many things to existing circuits without doing it properly. I think both fans are running off the same 15 or 20A fuse. I'm just a little hesitant about tearing everything out 1 week before I leave for the roundup in Paragon. But it would be better than being dead on the trail there.

 

[bronco69drp]

chances are broncnaz is right on. i will bet your new alt is capable of suppling the amps that your system actually can use. where as your old alt could barley put out close to what your electrical system needed to run all your accessorys at all. try running each high amp draw system off its own fuse(i.e. fuel pumps, fans, lights etc).
i use all relays for my high amp draw electronics.

 

[Wes harden]

If I read Marc's post correctly the 30a fuse that blew only protects the battey feed to a second fuse box, so as long as the fuse is close to the source, and the wire rating's and connections are good a 50a fuse should be fine. I would move the feed wire from the batt to the hot side of the starter relay, sorter run.

 

[BroncoMarc]

Here's a quick wiring diagram:

 

[SaddleUp]

Here's a quick wiring diagram:

Based on that I would say move the fans to their own circuit. Use the current wires for them to instead trip relays and you will have a lot less amperage flowing through that long 10 guage wire. The wiring to do this should be pretty simple since it basically amounts to running 2 wires to the fans and putting fuses and relays in those wires. Then the wires that are now running to the fans just need to be moved to the relays. The only other 2 connections are the grounds for the relays and that very well may fix this without rewiring everything.

 

[Bronchole]

As to the why it blew now, your old charge system by your testomony was running at 11 volts when fully loaded, your new system is probably running at a higher voltage with the same load. When electronic stuff gets more voltage it draws more current.

BTW, I assume that your fuse blocks are ATO type fuses (mainly because I haven't seen any 4 fuse maxi fuse blocks) the largest ATO fuse I have seen is 40A and they are not common. I'd just run another 10 ga. lead from the battery to another block for the fans, replace the blown 30Amp fuse and call it a day.

 

[bandit]

I just got my 3G conversion done and I fired it up for a test. I turned on most of my electronics (2 fans, fuel injection, headlights, arb valve) to give it a test. My original alternator had me down to 11 volts since I added the 2nd fan. All was going good for about a minute, then my main fuse blew. It didn't just blow.. The plastic was slightly melted.

All my wiring is custom since I've been buggyfied. I've got a main wire going from the battery to fusebox A. It goes thru a 30A fuse, then thru a big relay switched my by ignition switch. The relay powers up fusebox B which all the accessories are tied into.

It was the 30A fuse that blew. The 3G is the only change I've made since adding the 2nd fan a month ago. It ran fine for a week in Moab with the 2nd fan. I never blew that fuse with the original alternator.

Is 30A not big enough for 2 fans, fuel injection, minimal lights, cb, etc. ? Have I just been underpowering all my electronics with the original alternator and that's why it never blew?

Just a thought;I had a melt down before a fuse blew,and the culprit was a loose connection.Sometimes a loose connection can turn it into a soldering iron.
BANDIT

 

[BroncoMarc]

Below is a diagram of my plans.. I picked up some 40A fuses today and some relays. I was going to try it today, but it was raining too hard and my Bronco doesn't fit in my garage any more. %)

 

[Wes harden]

That will work, just make sure to put a fuse or fuse link in at the soleniod.

 

[BroncoMarc]

I finally got it all set up. The fans are on their own relays and the 30A fuse is now a 40A.

I put my meter in place of the fuse to see how much I was really drawing. Here's what I found:

3.5A EFI w/o fuel pumps
5.5A Headlights / LED tail lights
.15A /ea Relays for fans
around 9A Fuel pumps
---------------------------------
19A total with everything on and engine running

I'm pretty sure that would be over 30A with the fans on. I was pretty close to the limit before I added the 2nd fan. I wonder if it survived the week at Moab purely because the old alternator was underpowering it.

 

[broncnaz]

I would run a seperate power wire for each fan from the battery just to be on the safe side but otherwise your setup looks fine.