Re-wire truck or???

[Houston Ben]

Hi all,
My wiring is not the best and im thinking it most-likely needs redone. If I turn my A/C on the volts drop a lot, if I roll my window down the volts drop, If i turn my lights on my volts drop, if my electric fan turns on my volts drop. I have relays for both fans, but they still seem to draw a lot.

So, do I need to re-wire? do I need better/thicker gauge power wires for the other wires to draw from?

What is yalls experience in this??

Thanks for any help!

[gmachinz]

What kind of charging system upgrades have you done? I'm actually in the process of building several harnesses for members at the moment but I have some time to answer some of your questions. Obviously with added components the charging system begins to take a serious hit and while new harnesses may not be absolutely needed, upgrading to a high output charging system would help get the most out of everything.

[Houston Ben]

Hi gmachinz,
Thanks for responding. I do not know what you mean by charging system, are you talking about the alternator? If so, I LS swapped to a 2011 5.3 with stock alternator. Other than that, there is not much to it. Power windows, power locks (don't work), radio, and e-fans.

Any idea?

[gmachinz]

Ok...so there should be a single 12V switched IGN lead that "turns on" the alternator. Then, you should have at least an 8ga (or larger) main charge lead going to your main firewall junction. From that point is where you need to make ALL of your power runs. With everything you've got going on, I'd say you should have a 4ga main supply charge lead. Do you have any detailed engine bay pics?

[hatzie]

The stock charge wire on the LS1 F body is 6AWG. 6AWG will carry 100amps just fine. That should be plenty.
http://www.powerstream.com/Wire_Size.htm
Yes the alternator is MAX rated for 105-145amps but it rarely will run more than 2/3 of the rated current. The battery and alternator will not last long if you are pulling close to 100% rated output continuously. They aren't designed for that.

The first thing I'd do is break out your good meter and run some static voltage drop tests to isolate which cable is causing the problem.
Check from the battery to the engine block circuit and the battery to the alternator BAT circuit with the ignition on and engine off. If you have larger than .1vdc drop then try to isolate which connection is loose by testing at each connection point running back toward the battery. I bet you'll find a dodgy cable or loose/corroded connection. Fix em and you'll have a more stable charge.
#2 would be to make sure the Sense lead to the alternator regulator connection or the PCM is making good contact at each end and is not damaged or spliced in some dodgy fashion.

[Houston Ben]

Thanks for the replies GMmachinz and hatzie. I will have to check what gauge I am running to my firewall junction and then look for the lose and corroded stuff. My wiring at the junction is not pretty and I have been meaning to redo it. I will look at all this probably tomorrow (kids and sports) let you all know what i find.

Thanks again.

Ben

[tucsonjwt]

I am no electrical wizard like the others, but I have done a couple of things that helped my old 83. If you up upgrade to a larger alternator (and add appropriately sized larger cables - the other guys can tell you what size), then I think you will have a good start. The stock alternator has very little output.

My biggest electrical problem has been 30+ year old harnesses and connectors which have dried out over the years and no longer make good contact. This was especially a problem for the heater control and power windows and power locks. If I were you, I would start with the alternator upgrade and take it from there. I bought mine online and had to tweak the mounting bracket and get an adapter connector but it has been working well for about 10 years.

[Dead Parrot]

Don't overlook the possibility that your alternator has partially failed. If one of the stator wires has blown apart, you will get some output, just not a lot.

Might also clean up the connections on the alternator. A bit of corrosion can cause a lot of voltage drop.

[franken]

We need actual voltage measurements and where they were taken to even start to guess. What's the battery voltage measured at the battery using a DVM? Same question w/ the engine idling? Same Q at 2k RPM?
Rather than an expensive wiring harness, I'd start by cleaning contacts, and fixing cheap ground connections.
If a certain thing, such as locks don't work, then its time to figure out why that bit doesn't work.
An LS most likely has a higher V (check the voltage in your new car vs an old one) output alternator. If you haven't changed/fixed the wiring in the old truck, you most likely have connection and ground trouble.
Alternators are typically rated in Amps, meaning Amps at X voltage, but the load is typically less than what the alt can produce due to resistive connections limiting current.

In short, you can connect it to Hoover Dam, at the right reduction and rectification, but the load (wiring, switching, etc.) is the trouble.

[hatzie]

More modern alternators do not have more volts output than the older alternators. Charge voltage for a 12v battery is 14.5v DC no matter what year, make, or model it is.
The stock 73-91 CK & RV trucks came with SI series alternators that have a max current capacity of 65-94 AMPs at 14.5v DC.
The AD series alternators that come stock on the LS motors have higher current capacity, 105-145 AMPs, but they are still 14.5v DC output.

A piece of trivia... 6v batteries charge at 7.2-7.4v DC and 24v battery packs on transit coaches and commercial trucks charge at 27.6-28.2v DC.

Since this is a conversion from a smallblock to LS motor I would look to see if the ground straps from the frame to the block and the RH head to the cab were actually installed.

[Houston Ben]

Hey all,
Thanks for all the suggestions and I will be doing some test on with a volt meter this week to see if I can find where it is dropping. I had a SNAFU on the way home. My volts were way down and the battery just took a crap on me. I believe this was all my fault as I jerry-rigged my alternator wire to my battery and the wire was burnt black. I had planned on fixing it but it had been running that way for 3 years... oh well. after having to push my truck out of traffic and installing a new battery and new 4 gauge wire from alternator to batter I was up and running. I had the alternator tested and it is still good but volts still dropping when I am using power for anything other than the engine (i.g. windows). Here is a pic of where most of my wires are connecting and it is not a pretty site I will admit.



I will clean this up, re-look /do the grounds and see what happens.

Thanks for the input all.