Accessory wiring/junction block

[77 K20]

Wondering what to do here... all of the accessories I have added (and previous owners) have been wired directly to the battery. There are lot of wires to the battery now.

I recently put in a larger alternator and it didn't help much at all. In doing some reading I found that the alternator companies recommend that all accessories come from a junction block away from the battery. Then run a big gauge wire from the back of the alternator to the junction block.

I know there is a factory junction block on the driver's side near the brake booster... but that is very far from the battery where all the accessory wiring is already at.

My idea is to remove all the accessory wiring from the battery and put it nearby on a junction block right there. Then run a 8 gauge wire from the new junction block to the existing junction block near the brake booster.

Is there a flaw with this plan? Or am I missing something? Just want to do this once.

And where does the voltage sense wire from the alternator go? Think I heard once it goes to the horn relay? Why would it go there? Shouldn't it go to the factory junction block near the brake booster?

The volt gauge drops down at night with the headlights on, fan set to medium, and the wipers on. The truck has good grounds everywhere already.

 

[Camar068]

There was a post regarding updating the wiring. Sorry I haven't seen it in a while so I can't post a link. I think HR or Retro posted it. Term related to "a must upgrade" or something of the sort. I thought it was a sticky, but maybe not. It had to do with updating the wire sizes here and there I think.

That may help with the gauge dropping.

Also, you could wire up your headlights to run w/relays off the battery. That should help, but can't give a definite answer as I haven't completed mine yet.

Yeh you could relocate or add a junction box/terminal strip for all your accessories. Someone posted one that was on the backside of the glove box, hidden out of the way, but easy to get to for interior needs.

 

[77 K20]

HotRodPC has a post called the "Big Three" to upgrade the electrical system. It involves putting a new thick wire from the alternator output to the battery/junction block. Then to clean/fix the negative battery cable, and then check the engine block ground. I've already taken care of the grounds.

Didn't say much about where to draw 30+ amps of continuous draw from. (headlight upgraded harness, electric fuel pump, TBI computer, fog lights)

Just need to make sure things are done as "correct" as possible. I use this vehicle in the back country where there isn't even cell service. Reliability is the #1 concern.

I've read pulling the accessory loads from the battery itself can drop the life expectancy of the battery down to 2 years or so. And being that I have an Optima battery if the battery gets drained down there is a very low internal resistance in the battery itself and that puts more stress on the alternator.

In fact, quite a few battery chargers won't even charge a Optima if it is run down. Shows the battery as shorted. (I've run Optimas for quite a few years). I now own a battery charger made by Optima itself to charge them. No issues.

 

[Camar068]

Thx 77, that's the post I was talking about.

 

[77 K20]

So I found my immediate problem. About 2 days ago I replaced my alternator with 12si (instead of the 10si). I started the truck after the swap and verified the battery was charging.

Today I drove it to work in the evening with no lights and it was only showing 13 volts at the voltmeter. At lunch at dark and in the rain it was 12 volts. Turns out the 6 gauge wire I had going to the frame had the ring lug crack, break, and fall off. I put a new ring lug on it and it is better.

But I still need to clean up the wiring. I have too many wires to the battery and I figure there is 35 amps being drawn from those wires alone. So I need a terminal block to mount all of them to. And I think the alternator sense wire should monitor these, not something in the cab.

 

[Green79Scottsdale]

Electrical is not my strong suit, but in my head this is sound logic. Do a little research on some of the newer trucks and see how they are set up. I am thinking of more 88-07 years, ones that would be in a junkyard. It seems like they would have it set up to where the main battery lead goes into a junction and splits off from there. Once you figure out what they use, get one through a yard or order a new one online and put it into your truck. Like I said, electrical is not my thing, but I am trying to learn!
@RetroC10Sport and @gmachinz would be great guys to run this by.

 

[77 K20]

Well- after doing a ton of reading and then staring at the truck and my 2003 Silverado I did some work on it. First I used my meter and did some measurements.

With fan on high, high beams on, wipers on, truck running I had 13.4 volts at the battery and 13.85 volts at the factory junction point near the brake booster. But with just the high beams on there was 13.7 at the battery and 14.2 at the junction point. So that told me the alternator couldn't see what is going on with the current demand at the battery.

I wired a 6 gauge wire from the alternator to the junction point. With everything on I took more measurements. 13.65 at the battery, 14.19 at the junction point. Better! But the battery still was being left out...

I wired a 6 gauge wire from the factory junction point to a trailer junction block on the passenger firewall I put in years ago for my 5th wheel. This then leads back to the battery. With everything on I now had 14.41 at the battery, and 14.47 at the factory junction point.

HOWEVER... my volt gauge inside showed probably 12.8 volts only. I'd like for it to be able to be more accurate. I'm guessing the small red wire on the 2 prong plug on the alternator feeds thru that square passthru connector and goes into the cab and somehow goes to the volt gauge. Maybe the firewall connector has a bad connection? Or the whole fuse block itself in the cab isn't running at 14+ volts. I don't know where the fuse block gets it power from.

And I do not have any accessories or major power draw in the cab. The radio looks to be a 30 year old piece of junk that I don't even use. I have added 3 gauges though. A tach, outside air temp, coolant temp gauge.

 

[77 K20]

So spent a few hours out working on the truck last night. I found out that the firewall electrical plug under the brake booster area comes apart if you undo the bolt that is in the center of it. Never have taken it apart before. Inside looked like chocolate syrup everywhere. I'm only guessing GM packed it with some kind of grease back in the day? Used electrical cleaner and cleaned everything off so I could see the contacts. Most looked really good. Used some emery cloth on a few to clean them up a bit. I then used some electrical cleaner that leaves a protective coating and helps promote electrical contact and put it back together. Started up the truck and turned everything back on and now the volt gauge looks to be reading around 13.3 volts or so. I'm happy with that.