So why did this catch on fire? ... again.

**BigHairyMonkey** · #1 (**permalink**) 06-15-09, 02:46 PM

I have a 3g alternator setup in my car. Everything is wired correctly as it should (i believe). The problem ive been having is that for some reason the power wire ends up literally burning through at different locations. I have no idea why the hell this is going on, ive checked to make sure the ground is clean and that everything is wrapped correctly with no shorts. The 3g is 130amp unit, and i have a small 600watt amp (music) + SHO e-fan set on low speed through a fan controller pulling amps + the rest of the electrics.

Last night i was driving and and the alternator shut down again and i immeadiatly knew there was about to be a fire, i pulled over real quick and sure as **** a little baby fire is going on right next to the inline fuse. I put it out, bypassed the Fuse and limped the car home. I need to figure out what the hell is going on as this is my daily and i cant afford to be stuck on my way to work.. etc. This is the third time this has happened and ive, unwired and rewired everything 10 times over.

I've attached a cute little picture depicting my hardships

The first time the wire burned through it happened right where the power wire meets the alternator. The second time it was at the ANL fuse INPUT on its way to the starter relay. Last night it burned up at the ANL output on its way to the starter relay. I've marked all this on my da vinci schematics.

I dont know what the hell is going on, its probably due to some ignorance on my part and hopefully you guys can steer my in the right direction.The only thing i could imagine it to be is i haven't gotten around to upgrading the ground wire that runs from the drivers firewall to the block so it is the stock size. My power wire is a 4awg.

Let me know what you think guys, thanks.

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HISSIN50 · #2 (**permalink**) 06-15-09, 04:03 PM

How are you making your terminal connections on the charge cable? Sounds like they are problematic (resistive, which creates heat, which creates more resistance).

The last thing you should do in that instance is to remove or bypass the fuse. In the future, I would disconnect the regulator plug and open (and insulate) the charge cable, and drive home on battery power instead (if it's safe and you can do this. If not, tow it home).

90blacknight · #3 (**permalink**) 06-15-09, 06:08 PM

Did the fuse blow? Did you keep reusing the same fuse holder? I'm guessing the cheap china made fuse never blew.

Regardless, even if the fuse blows, the bit of wire on the alternator side is still unprotected (so is the bit after the fuse incidently) which is what you saw when it melted the first time. I'm guessing the second and third time were a direct result of resistance caused by the fuse holder/fuse itself. I'm not a believer in putting a fuse on this line (I'm going to hear sh** for this), because you can still fry the alternator and the line can still catch fire. I'd rather have a good quality large gauge wire with no interruptions.

**jrichker** · #4 (**permalink**) 06-15-09, 06:08 PM

Solder the lugs in place on the wires.

Many of the audio grade fuse holders are made of plastic that will not withstand the under hood temperatures. They soften up and the plastic flows away from the bolts that secure the fuse and lugs. This allows the connection to loosen which creates resistance which creates heat.

Try this instead:
Fuse holder from local NAPA dealer - Item#: BK 7821143 Price: $10.49
Product Features: Thermal Plastic Holder For AMG Type Fuse Rated From 100 To 300 amp
part numbers are 782 1143 (fuse holder) and 782 1137 (125 amp fuse) at NAPA

**BigHairyMonkey** · #5 (**permalink**) 06-15-09, 06:18 PM

all valid points, thanks gents. So as far as the consensus, fuse or no fuse on the power wire?

**aar0s** · #6 (**permalink**) 06-15-09, 06:25 PM

oh noze! thats the same way that mines been wired for over a year now! Thats not the kit that LMR was selling for like 50 bucks or so is it? Ive got my fuse tucked inside my finderwell behind the battery away from underhood temps. no problems thus far.

**jrichker** · #7 (**permalink**) 06-15-09, 10:34 PM

Quote:

Originally Posted by BigHairyMonkey

all valid points, thanks gents. So as far as the consensus, fuse or no fuse on the power wire?

Always use a fuse. If the alternator develops an internal short circuit, the fuse will blow and prevent a really serious electrical fire.

WhiteSSP · #8 (**permalink**) 06-16-09, 04:51 PM

Subscribing. I also have a 3G alternator on mine, and my fuse blew last weekend (130amp ANL fuse) so I just hardwired it to the terminal on the battery until I can find another fuse (apparently 130amp is an oddball fuse, i went to two audio shops, all the big box auto parts stores, two big rig parts stores, and a boating supply store, and no one had them). Mine blew because the wires on the alt were loose (or so it seems, tightening them back on it fixed the problem), but other than that I cant explain it.

1991vert · #9 (**permalink**) 06-16-09, 05:05 PM

is the alternator charge wire and the + battery cable connected to the same post on the starter solenoid? i cant tell by your diagram.

Darkwriter77 · #10 (**permalink**) 06-16-09, 05:15 PM

Quote:

Originally Posted by 1991vert

is the alternator charge wire and the + battery cable connected to the same post on the starter solenoid? i cant tell by your diagram.

Yes.

**jrichker** · #11 (**permalink**) 06-16-09, 09:33 PM

A 125 amp fuse will be fine and shouldn't be hard to find. Fuses have a wide range tolerance, so 5 amps isn't going make much difference in how things work.

1991vert · #12 (**permalink**) 06-16-09, 10:28 PM

Quote:

Originally Posted by Darkwriter77

Yes.

looking at that diagram, it looks as though the wires are not on the same post, rather one on the post it's supposed to be on and the other on the post for the starter wire...

**jrichker** · #13 (**permalink**) 06-17-09, 09:16 AM

Electrically speaking, if the cables & connections are all in good condition, it makes no difference if the fuse is connected to the battery postive post or the battery side of the starter solenoid.

Here is what I would recommend just to keep it neat and grouped together:

Starter solenoid wiring for 86-91 Mustang

Starter solenoid wiring 92-93 Mustang or earlier Mustang with upgraded high torque mini starter.

1991vert · #14 (**permalink**) 06-17-09, 06:17 PM

so you're saying it's okay to run the alternator charging wire to the post for the starter? that's how it looks wired to me. hopefully the OP can clarify how he has it wired.

HISSIN50 · #15 (**permalink**) 06-17-09, 07:05 PM

No, the charge cable needs to be connected to the battery's positive post or a remote positive battery post (like the battery lug on the starter solenoid). Whether the alternator cable goes directly to the battery or to the remote location (where a 4 or 2 AWG cable transmits power back to the battery) doesnt matter (it can with some PWM devices, but not with an alternator).

If it was wired how the diagram depicts, he'd have had a thread up a lot sooner about how the alterntor doesnt charge.

1991vert · #16 (**permalink**) 06-17-09, 08:15 PM

true just looked weird...

**93 LX** · #17 (**permalink**) 06-18-09, 01:43 AM

maybe 2 or 0 ga wire would help with the heat issues.....

**tmoss** · #18 (**permalink**) 06-18-09, 09:43 AM

Quote:

Originally Posted by jrichker

Solder the lugs in place on the wires.

Many of the audio grade fuse holders are made of plastic that will not withstand the under hood temperatures. They soften up and the plastic flows away from the bolts that secure the fuse and lugs. This allows the connection to loosen which creates resistance which creates heat.

Good advice - and DON'T be tempted to use a connector that is too small for the wire guage you are using - match the wire guage and connector size, crimp and solder.

**Strype** · #19 (**permalink**) 06-18-09, 10:04 AM

Did I ever tell yall how happy I am since I ditched the Taurus fan and went back to the stock fan