Help find the missing link

[memo43]

Ok here goes
my truck is an 85 k20 with all stock gauges (no dummy lights)
I recently did an engine swap original 350 for a l31 350 (roller motor)
while I was at it I installed a summit max efi system.
New battery, new alternator.
The engine has the serpentine belt system. With that being said it had a CS130D alternator, which I thought was bad, changed it for a CS144 (140 amps) to supply all the upgraded electronics.

Now my issue with the truck off the battery reads 12.8 volts, with it running It reads 14.3
same reading at the alternator.
I have a relay bank by the headlights that powers the headlight, hi/low
dual ford Windsor fans. I get 14.2 v there as well. same for the bus bar that is tied to the battery (10 gauge)
My Voltage gauge in the cab reads 13.2. tested a few circuits at the fuse panel
some get 14.2 the majority read 13.2.
Only wires I change are the factory wires that go to the battery terminal, upgraded with 10 gauge wires. ground is ties to block and frame.
Main battery cables I upgraded to 4 gauge both positive & negative.
Alternator battery stud goes straight to the battery positive with 4 gauge wire as well.
I'm using the correct adapter for the alternator with the resistor in the L terminal, "S" terminal or sensing is 10 gauge to the right side of the junction block (as you are looking at it)

while driving I avg 13.4-6 volts. while driving at night if the fans kick on the headlights will dim.

Is there a wire that I'm missing (missing link)
(1)power wires from fuse block to starter is 10 gauge.
(2) starter to junction block is 10 gauge.
(3) alternator to battery is 4 gauge
(4) battery terminals are 4 gauge


what is the missing link or better yet how do I get the 14.2 volts to the fuse box to distribute to the entire electrical system.

thanks in advance

[VetteVet]

I know we talked in PMs and I told you what I thought was the problem but I see that you are still not getting enough voltage and it appears that you have done the right wiring. I have had a thought that the adapter that you have on the L wire may have a resistor that has too much resistance in it. This might prevent the regulator in the alternator from putting out enough amperage into the alternator fields for your loads.

Painless wiring recommends an 85 ohm- 5- watt resistor for the conversion to a 10/12 SI and most of the guys have used up to a 300- ohm 1 watt resistor for the CS alternators. I have seen some recommendations for resistors as high as 500 ohm but that seems a bit too high, it's a shot in the dark but i'd try a smaller resistor unless you already have a lower value installed. That 144 should be more than enough to handle your needs so I would take it back and get a replacement.

[franken]

Measure the battery voltage with the engine running and not.
My guess is you're chasing a nonexistent issue since the charging voltage is higher than battery voltage and the battery shows charged.
You also didn't state a problem.

[bhap]

One option would be to run the power wire from the alternator directly to the distribution block and then to the battery rather than directly to the battery. If I read correctly, your junction is fed from the battery so when your fans kick on, the power comes from the battery and not directly from the alternator. Getting your battery out of the middle should improve the response from the alternator when the S wire on the distribution block sees the fans asking for amps. Have you looked at Madelectrical.com? The distribution block should be the main junction for the system. Running power from the distribution block to the fuse block should shorten the distance and also send power more efficiently from the alternator. This should keep the lights from dimming. One comment you made makes me want to ask about the terminals in the fuse box- are your terminals dirty or corroded? All of the terminals in the fuse box should read pretty much the same.

[memo43]

Vettevet
thanks for the reply I will try and switch out connectors with smaller resistors.
So this illustrious brown alternator wire, is there a corresponding fuse or wore that goes to the voltage gauge on the inside of the cab. I know you mentioned an ignition source 12 volt, there are spots on the fuse box that I can run an ignition hot to the L terminal. in other words replace the Brown wire and start from scratch. S terminal going to the junction block right side stud as I'm looking at it from the front, this is the correct spot?


Franken I've measure voltage at the bat with the truck off I get 12.6 volts
with it running I'm getting 14.2
Same results at the alt battery stud.
My issue is when the engine running I'm getting 14.2 volts at the engine side. inside the cab I'm getting 13.5 once I start using the elec fans, headlights etc etc my voltage drops.
I'm just trying to figure out how to get the full 14.2 voltage at the fuse box to power all my accessories.

[memo43]

bhap
I'll try running both (power wires) to the junction block and see what happens

[VetteVet]

Originally Posted by memo43

bhap
I'll try running both (power wires) to the junction block and see what happens

I think you are on the right track and with Bhap's suggestion you should see some improvement. Franken is right about the voltages and as he says, your system is working but you are seeing some voltage drops in the headlights and
possibly some other loads as well.

There is a common belief that the alternator is just there to charge the battery and the battery is the main power source. Actually the opposite is true. The alternator is much more capable of suppling amperage to multiple loads than the battery and it will supply the same amount of voltage to all if the wiring is correct.

You're system uses the voltmeter to measure the voltage at the point in the wiring where it is connected. This may be less than the actual voltage in other parts of the circuits, which is what you are seeing.

To answer your Question. The L wire can be supplied by any 12 volt source including the battery positive post as long as you remember to wire a resistor in series with it to protect the diodes in the alternator. The word is that the resistor must be at least 35 ohms. Most professionals would say that you should use at least double that to be safe. The factory used a 10 ohm resistor in the 64 to 74 year trucks. They accomplished this with the charging light and the resistance wire off the key switch in case the light bulb burned out. It would back up the resistance and also provide a circuit to the alternator. The gauge dashes didn't have the light but they do have the wire.

I'd have to check the 74 and later models to see what they used. If I see it in the diagrams I'll post it.

Before I forget to mention it, if you run a L wire directly off the battery positive post you must install a cutoff switch in the wire as well as the resistor or else it will drain the battery overnight and might harm the alternator. I only do it that way for troubleshooting.

When I installed the engine in my truck, I actually wired the alternator from a battery positive source a as well as the starter and ignition so that I could work from the engine bay and not have to run back and forth to the cab. I di install a switch in the wire for battery protection as I stated above.

In your case I would go to a main key on, power source, and install the resistor in the wire or use your adapter and you could replace the L wire.

[memo43]

Thanks for the indepth response Vettvet
I will post a pictures of my wiring diagram an if all checks out
I may just be chasing a ghost. Or another maybe another set of eyes in my witing might reveal the missing link.

[kwmech]

You should have more than 12.6 volts at the battery--even after sitting for awhile. Should be closer to 13 or even 13.5 What is the CCA on the battery? Also main battery cables should be 2 ga not 4. 4 ga would be for a subaru or toyota. Does not sound like you have a charging issue. But I would double check all the ground wires. Battery to engine block, block to frame, battery to body. I think, factory wise, there were either 2 or 3 different body/ground wires. Early chevys even had engine to body grounds. With engine running you have the same 14.2 inside the cab

[memo43]

Ok as promised here are some of the photos to show what I have going on.
Alt plug shows "L" wire with the inline resistor connected to the "brown alt wire", as well both the 4 gauge wire going to the battery from the battery post and the 10 gauge wire going to the junction block.
Battery connections nothing fancy
Junction block with one pink wire coming from the blower
one 10 gauge wire coming from the alt, the other coming from the starter stud
key on fuse bar, this fuse panel is powered by a 30 amp relay that handles ign on for the headlights, elec fans and efi key on source.
Rough attempt of my artist skills showing what wires I have going were.
Final one is the read out from the handheld from the efi control panel showing rpms and volt readings. The volt gauge on my dash reads about the same

Does any of this seem wrong?