Positive and Negative battery cable questions.

The negative cable is correctly connected. Just make sure that
the metal is clean and shiny when you put the new cable on.

Be sure that you connect the negative pigtail to the body ground.

1.) The main power ground is from engine block to battery: it is
the power ground for the starter & alternator.

2.) The secondary power ground is between the back of the
intake manifold and the driver's side firewall. It is often missing or
loose. It supplies ground for the alternator, A/C compressor
clutch and other electrical accessories such as the gauges.
Any car that has a 3G or high output current alternator needs
a 4 gauge ground wire running from the block to the chassis
ground where the battery pigtail ground connects.
The 3G has a 130 amp capacity, so you wire the power side
with 4 gauge wire. It stands to reason that the ground side
handles just a much current, so it needs to be 4 gauge too.

The picture shows the common ground point for the battery & extra 3G
alternator ground wire as described above in paragraph 2.

The battery common ground is a 10 gauge pigtail with the computer ground
attached to it.

Picture courtesy timewarped1972


3.) The computer has its own dedicated power ground that
comes off the ground pigtail on the battery ground wire. Due to
it's proximity to the battery, it may become corroded by acid
fumes from the battery. It is a black cylinder about 2 1/2" long
by 1" diameter with a black/lt green wire. You'll find it up next to
the starter solenoid where the wire goes into the wiring harness

why do you need autozone to tell you how long your cables are? Just measure the length, and go buy cables that long.

JH96GT said:

Thanks.

One question though, negative pigtail to the body ground? What negative pigtail? I know dumb question, but I'm not seeing it. (fwiw it's an 86).

Click to expand...

Some applications have a small (12ga) wire from the negative terminal. This can be used for the body ground. Other applications use a strap from the cylinder head to the body. Still others use both as Ford determined there was a need to have an isolated ground to some electronics. It's important that the body has a good connection to the battery negative as many devices use the body as thier ground.

Not sure about the 86. It's been a while since I owned one but you need to make sure you have at least one good connection from the body to the battery negative.

For those of you whose cable may be missing or damaged, here's what the OEM cable looked like:



Many aftermarket cables only had the 10 gauge body ground and didn't have the computer ground. In that case, make sure to crimp or solder a log on the computer ground wire and ground it to the same place as the body ground.

Ok I want to be sure im clear on this. My negative cable don't have the wire that goes to the chassis of the car, just the one down to the block. But I do have the ground strap at the back of the engine to the firewall. Should I add a ground from the negative wire to the chassis of the car also or will I be ok with just the one ground strap in the back. Also I have a 3g alt and its just the little stock strap.. I should probably upgrade that also..