Cable gauge from firewall fuse block to battery +?

Hello, my car is an '03 and thanks to a leaky Interstate battery, the positive battery clamp turned into green mush. I need to replace the battery and am going to have to re-terminate the cables to hook to a new battery. The wire going from battery to engine compartment / kill switch was easy enough to remove and I'm guessing is 4 gauge, so I'm just going to take it and have a new one made with similar ends. The second wire goes from battery to a block on the firewall behind the driver, probably about a three foot cable run, but to get it off that fuse block, I'm going to have to raise the car and take part of the bottom pan off. In the mean time, I was curious if anyone knows what gauge cable that one is? Just eyeballing it, I'm thinking 2 but until I can get the car apart and remove it, hard to tell, and I'm wanting to go get the cable made tomorrow before Christmas weekend since I'll have some time.

 

Thanks!

Truthfully, 2 or 4 sounds small to me. Knowing you're spinning over a decent size motor, I would get a 2/0 (aka 00) cable made for the ground strap.

Truthfully, 2 or 4 sounds small to me. Knowing you're spinning over a decent size motor, I would get a 2/0 (aka 00) cable made for the ground strap.

 

As long as it physically fits, the bigger the better.

Well I got her running again.

 

So turns out the power cables are all 4ga after all, I just thought one was larger after mangling it with too small a wire cutter when removing the melted terminal. I found a handy diagram on bullstuff; electrical system diagram 61.02.00:

 

https://www.bullstuff.com/lamborghini-parts...pe-usa/61.02.00

 

So turns out here's how the Murci is wired:

 

4ga from alternator to the 250A "mega fuse" in the engine bay just under the battery disconnect.

4ga from mega fuse down to positive battery terminal

4ga from positive terminal to fuse block on firewall directly behind driver

4ga from that fuse block to starter

4ga ground from negative terminal to battery disconnect, and then to frame

 

So the battery disconnect actually disconnects the negative side. I had always assumed it was tied into the positive since the fuse is directly below it.

 

Now, here's the catch22 I had. With OEM battery terminal melted, I no longer had two terminated cables to connect to positive terminal. With no way to connect a new battery, there's no way to use the car's lifting system to raise the front end to get a floor jack under it. With no way to put it up on jack stands, I've got no way to replace the cable run to the firewall fuse block because that requires removing one of the bottom panels of the car forward of the rear wheel.

 

What I ended up finding at O'Reilly Auto Parts is a "Super Start - Top Post Battery Cable Splice" for $17. It's a battery post clamp with two 6" length of 4ga cable connected to screw down cable blocks. All I had to do was cut off the two car power cables to get a clean end, stripped off about 1.25" of insulation, inserted, hex key to lock them down, electrical tape and heat shrink around them. Car fired right up.

 

I plan to go back and fix things correctly though regardless. Bullstuff sells the complete wiring harness for this, part number 0061008156, for $20. It is the dual positive battery terminal and boot with the 4ga cables that go out to the firewall fuse block and the engine bay fuse block. Now that the car is running, I'll be able to raise the front end and jack the car up enough to remove the bottom panel and replace the cable to the firewall fuse block.

 

Good times... lol

I never lift the car to get the jacks under it. I have 3 of these to lift the car up and then put it on jack stands almost 2 feet high:

 

http://www.harborfreight.com/automotive-mo...pump-61282.html

 

I always lift the rear up first so the rear wheels are off the ground and then I do the front left and right alternative a little bit at a time, and the chassis doesn't get stressed since it pivots on the rear jack with the rear wheels staying off the ground.

 

Those jacks often go on sale.