therotaryrocket

Me and my friend are about to replace his alternator charging wire, in the Haynes and from what it looks like the wire goes from the alternator to the rearward side of the engine bay fuse block (main 80 Amp fuse). Except the wire goes down into a harness/loom that goes by the starter, so I was wondering because there is no power steering in the way could I just take a 10 gauge wire from the alternator straight to the back side of that 80 amp fuse? Is 10 gauge ok? His voltage is pretty low and it has a NAPA remanufactered alternator, we already had some other wiring problems so this seems like a good thing to do. With the heater on max, the headlights burning, and the brake pedal depressed the voltage goes below 12volts. Using my digital multi-meter, I measured 12.5 volts with the engine off and running at basically any rpm with no accesories on it has just barely like 13.9-14.08 volts. His car doesn't even have a radio (stolen). thanks for your help, I didn't see any custom alt. chrging wire replacement in the search.

therotaryrocket

nobody knows where the wire goes after it leaves the alternator? I want to use a short length of wire (10 gauge) straight to the main fuse. Somebody help, this crap didn't look like it was in my Haynes manual or searching on this site.

sunshine

iTrader: (3)

Is there something wrong with the current wire?
If there is...just cut the harness and trace the wire. It loops around toward the starter, but then does a u-turn and comes back along the main frame rail and into the the main engine fuse.
-a

uRizen

iTrader: (2)

I need to replace mine. It was corroded enough to disintegrate on the alternator side and I had to rig up a temporary solution, so I've been thinking of just out-right replacing it.

By the sound of things it doesn't touch the alternator at all and just goes to the 80a fuse then, eh?

Icemark

Replacing the wire with a 10 awg wire is way too small. at very least you would want a 4 awg wire if you are replacing the wire. Remember you are running up to 80 amps through that wire. A 10 awg wire is good for about 20 amps... maybe 25 amps.

The wire runs down and back towards the firewall then leaps over neear the bottom rear of the drivers shock tower, then foward along the frame rail to the bottom of the underhood fuse box.

YearsOfDecay

Yeah.... What Icemark said..... It runs along with the wire that goes to the starter...

When I redid my electrical system... I ran a 4 gauge wire from the alt to a junction point on the shock tower.. from there, the battery hooks up and the starter, the fuse block and some other 12v relayed sources the bottom of the fuse box....

HOWEVER..... I took the whole friggin wiring system apart... if you just leave the stock wire in place and snip it off and run another wire to the box.... you could ground it out... be careful.... I'd suggest pulling the charging wiring harness out and actually re-vamping it

WAYNE88N/A

Also remember that there is a reason this wire doesn't run straight from the alt to the bus bar on the fuse block- this wire is constantly bending due to the movement of the engine itself, and a large "C" shape negates damage. If you do decide to run a new wire fairly well straight to the bus bar, put a "loop" in the run, much like some hydraulic lines are looped in the braking systems, to prevent the strands of the wiring from breaking at the bend radius...

Theoretically, a 10 gauge stranded copper wire is good for about 3000 watts, or 3000/12=250 amps in a 12 volt system. Just the same, 8 gauge would probably be the "smallest" cross-sectional area I would personally use if doing this job...

Icemark

Ah yeah... where are you getting this???

Anyone running a 1500 watt audio amp would smoke or over heat a 10 AWG wire in a matter of minutes.

therotaryrocket

the factory alternator wire looks like 10 gauge to me? anyways, thanks i'll put a loop in it and run 4 gauge, also i'm going to remove the old wire but im not running that path with the new wire. yea, the wire is corroded and spliced because i changed the terminal on the alternator side with not the best results. I think we'll probably change the battery cables as well. thanks again.

WAYNE88N/A

14 gauge circuit safely handles 1800 watts...

12 gauge circuit handles 2400W OK...

Straight out of the National Electrical Code book...

By interpolation, a 10 gauge circuit should handle 3000W...

It's the wattage, or power, limits that are determined by the cross-sectional area of the wire (gauge), not the volts or amps...

1500 watts in our 12v systems equals 125 amps flow...

1500 watts in our house wiring is 12.5A...

The same amount of power is "flowing" through each circuit...

Icemark

ahhhh yeah you are mixing up wattage and amperage.

And 1500 watts on a automotive system is 120 amperes. Not 125. Automotive batteries are 12.5 volts.

SAE wire ratings are considerably different than home/house ratings.

Multi-strand 10awg wire is only rated at 20 amps at 25 feet in automotive applications or 15 amperes at 35 ft. Of course sold core as used in Home applications is not ever recommended in automotive applications.

See home wiring guidelines don't take into consideration length, heat/resistance or vibration.

BklynRX7

I had a problem witht he same wires, the shop fixed it for me when they were doing something else, they also for some strange reason replaced the 80A fuse with a nut and bolt, kinda unsafe but i guess they knew what they were doing, and its under warranty anyways.

HAILERS

A nut and bolt in lieu of the fuse?????? Kooooool. Won't blow that sucker! humor

JamesBong

DANGER WILL ROBINSON! DANGER! Put that fuse back in!

uRizen

iTrader: (2)

No joke, that's fucked up if they just jumped the terminals. I don't see any reason why you would eb blowing an 80 amp fuse if you didn't have shorts anywhere.

Things like that are the very reason I do not ever bring my vehicles to the shop for anything but alignments.

strikland

damn dude, that's not cool at all. I hope you're just messing with us.


In relation ot the question, I had to replace the same wiring, because some jackhole cut into it while trying to perform some other half- assed wiring. All that's gone now. I replaced the battery cables and added a ground or two while I was at it. I figured while I had the loom apart, might as well stomp out a few potential gremlins.

robfeltner

I'm getting ready to do this also. I tried to buy the same wire that the factory uses, and cannot find it anywhere. I think it is actually an 8 guage wire. So, 8 guage alternator wires do not exist, but really nice bright red amplifier wires do exist, and about 10 ft of it can be purchased on ebay for 10 bucks including shipping. I just got some yesterday in the mail. This is the correct size wire. Note that 4 guage is the size of your battery cables. You might have a hard time with such thick wires.

Anyway, the alt actually has two cables coming off of the post...if you look. One goes to the back side of main fuse (80 amp) under your hood. The other snakes around and joins another wire around the shock tower (black with yellow stripe), that eventually goes to your fuse block inside the car. I agree that you should just snip the wires. The one to the engine compartment fuse block is a snap and will take you no time to fix. You may have to hunt around for the other. If I were you, I'd follow that second wire as far as possible and snip the old one and solder the new on in it's place.

Rob

therotaryrocket

the factory alternator charging wire looks a lot smaller than 4 gauge, i don't see why I would need to use it, besides i don't really know where to get it, we sell 2 gauge wire at advanced auto parts but thats really big.

cluosborne

The alternator fuse is the 80-AMP bolt-in fuse in the engine compartment fuse block. There are actually two leads that run from the positive battery cable clamp to two different fuse boxes.

One is 10 gauge and runs to the interior fuse box, the other runs to the engine compartment fuse box. The alternator supplies power through the 80 AMP fuse to the battery.

I've changed my alternator lead (which was 8 gauge) out with a Tefzel-insulated 8-gauge lead that runs shorter (if you run a longer distance, use a larger gauge cable). I used crimped ring connectors and heat shrink tubing. FYI, Tefzel is an anti-abrasive insulation commonly used on aircraft.

Frankly, I don't see the logic in running an important electrical lead from a fuse box, down near the starter and back up to the alternator. The lead itself is taped together with the battery cables and some of the wiring that runs to the starter and transmission sensors. You'll have to pull off the tape to get it out if you want to remove it. Or just unplug it at both ends and tape the leads off and run your own.

MAKE SURE that you run your new alternator lead through the 80 AMP fuse. If you're running a higher-amp alternator, you'll want to use a higher-amp fuse or circuit breaker (unless you want to blow a $5 fuse).

If you end up replacing your battery cables, go with an aftermarket set with molded clamps. OEM is prohibitively expensive and includes wiring you won't use. The positive battery cable will have a single 10-gauge lead--use that ONLY for the interior fuse box and run a separate length of 8-gauge (minimum) wire with a crimped ring terminal (with heatshink tubing to insultate it) to a another similarly crimped connector at the engine fuse box.

I got almost all my supplies and tools from www.terminaltown.com . The tefzel wire I mentioned is available in whilte insulation only and is cut to the foot. Gauges range from about 22 to 2 gauge. They also have some great heat shrink connectors that I used to all me to unplug the interior fuse box lead if I ever have to change battery cables.

cluosborne

Oh, and no soldering. It'll take forever on a 15-watt soldering iron and won't provide a lasting connection. Use crimp connectors and a proper crimp tool!

Last but not least, if you don't have that 80-AMP fuse and reverse battery cables, you could cause damage to your car's electrical system. I did that once and ended up only blowing the 80-amp fuse.

Chuckles

I bought 4 gauge wire with thick insulation from a excellent car audio shop for the charging wire and grounds. We crimped the eyelet connectors in a vise and then using a propane torch soldered them. Worked slick even though a little expensive with 28' of wire and 12 connectors totaling $54 and change.

robfeltner

Here's a thread I posted with the wires I put together today.

Rob

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/my-new-alternator-charging-wires-390826/

schexy1

Here is a link to wire size and amp rating. Remember, don't size the wire for a 12 volt system. A good alternator puts out any where form 14.1 to 14.5 with spikes up to 15 volts.

(http://www.powerstream.com/Wire_Size.htm)

WAYNE88N/A

That last link is no good- AWG wire gauges are different than the SAE gauges on our cars, as Mark alluded to earlier (I also used the wrong table with my earlier assumptions, my bad...)

Directly from the SAE site...Length of wiring run is not factored...Safe loads per gauge-

34 amps for 10 gauge
25 for 12 gauge
20 for 14 gauge...

And for you guys replacing alternator wires-
61 amps for a 6 gauge.

Remember, this is for SAE wire, not AWG

NZConvertible

No they did not...