Need help with grounds, stay positive cable

[Guy Dudebro]

In restoring my 67 c10, I'm having trouble mastering the electrical system. I have a slow drain on my battery somewhere and I think it may be an insufficient ground?
I had my battery charged and it was at 13.1. Next time I check, 12.7. Then 12.4 and so on.
I think maybe it was because I had the 4 gauge wire on the negative cable on the plastic of the fan shroud.

I attached pic of the positive and negative.

Questions:
Where should I ground the negative cable?

I took out the AC. So what should I do with the stray cable that DOESN"T go to the starter on the positive cable?

Any help is appreciated.

[kwmech]

Sure that is a neg cable in your hand? Appears to be taped to the original harness, and what happened to your small junction block on the fender?

[Guy Dudebro]

Im not sure I ever had a junction box. Is it usually inside the passenger side fender?

[franken]

First, a bad ground won't drain the battery, ever.
Next, which battery terminal is which? I'd guess the + side is closest to the fender?
Yes, the + cable goes to the starter and the - cable should be grounded to the block (yes, the block).
The wrapped one w/ the blue end is most likely a + wire.
You should look into a fusible link to feed the low current side, or you may soon be dealing w/ a smoked harness or worse, like fire. This has happened to me...
Normally there's a junction block on the fender by the battery where the low current side connects. That's most likely the red wire in pic 1, and where the fusible link would go.

[autocross]

Here's my .02. You should have several grounds. One should be Batt to engine block. Block to cab and Cab to frame. This configuration can be adjusted for aesthetics like Batt to engine and frame and engine to cab. If you have a large stereo or High output ignition system your ground should be the same size as the starter cable. I always upgrade my charge, starter and ground wire simply because the less resistance the cooler and more efficient it will work. All grounds should be the same size. If you have a drain on the battery it is usually a low grade short. Pull your fuses and ground one side of a tester on continuity and check each circuit for continuity to ground. with ignition off and all switches off there shouldn't be any.

[mike16]

remove all the fuses

install one fuse at a time. and see if the system drains the battery . if it does then you have narrowed the source of the drain to thta cicuit.

dont stop there

remove each fuse after you test that circuit

install the next fuse to test the next circuit

this is done because there may be more than one source of drain on the system

just remember to pull each fuse after testing that circuit.

follow that circuit around to each switch or component on that circuit test and eliminate them.

I had a factory underhood lite with a mercury switch. killed my old battery and was working on my new one when I noticed a bright light was on under my hood. the mercury switch was installed incorrectly and only went on when the hood was down. easy fix.

its usually the simple things

[franken]

Removing all the fuses is a bad idea. They're different so getting them back where they belong can be a problem once you have a handful of fuses. Not to mention, the issue could be under the hood.
First, find out if there's current flowing when everything is off or not. The battery may not be charged, or it may be bad. The usual test is to put a light in series between the battery terminal and the cable, or measure current at the same point.
Then make sure everything is turned off.
You can now start popping one end of fuses out, checking, reconnecting a fuse, and so on. Slow, but least chance of screwing up.
The alternator sometimes shorts a diode and can cause a drain. Might disconnect the batter, then the alt red wire, and retest.

[cooperhw]

Instead of pulling fuses I take the ground wire off and clamp a test light between it and the ground post on the battery. If it has a draw on it the light will be on all the time. Then take one fuse out at a time, putting the fuse back in if the light stays on. When you pull out a fuse and the light goes out, you know your parasitic draw is on that circuit. Figure out what's on that circuit and why it is drawing amperage. Stereos with memory or clocks draw some but not much. hope it helps.
Not saying it's right, just how I do it.