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CS130 alternator 1 wire?

MEMO43

MEMO43

1/2 ton status
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Mar 24, 2018
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Location
Gardenrville NV
Ok here is my dilemma
I have an 85k20 that I swapped L31 engine in
kept the serpentine system. Have added a summit Max efi kit to it.
New Battery AGM, New alternator but yet I'm not charging and my truck will shut off due to low voltage that the EFI requires
I'm running a CS140 alternator from orileys (140 amps)
I've replaced the positive cable from the battery to the starter with 4 gauge wire
same for the ground wire.
From the Fuse box to the alternator is 10 gauge, same for the wire that goes to the junction box as well as the starter.
I'm using the correct adapter for the alternator.
My issue is at the battery with the engine running I get 14.2 same as the power stud at the alternator bit everywhere else I get 12.3 all the way down to 10.2.
I've traced and tested every wire that I could think of and came up empty handed.So before I do the knee jerk reaction or rewire the entire truck

Is anyone running either a CS130 or Cs140 style alternator that is a true 1 wire and if so what is the part number and were did you get it from.
 
if you are getting 14.2 at the battery and the fuse box your alt is working. You have a resistance problem, my guess would be at the fuse box. Do you have 14.2 volts at the ignition switch 2 feed wires? How are the fuse links?
 
Wes I'm only getting those readings at the battery and behind the alternator (battery stud)
The fusible links were replaced when I redid the wiring to the starter/alternator.
You think/recommend I separate the fuse box at the firewall and clean out the contacts?
 
I would definitely take a look. It could all green or loose the black goop they use from the factory gets hard and crumbles.

I would still inspect the fuse links. The fuse links supply the power to the fuse box and ignition switch, from the starter battery lug.

What is the voltage at the firewall bus bar ?
 
Voltage at the bus bar is 14.2 as well
once I clear all the snow of the truck I'll recheck everything.
But this one is really beating me up
dam electrical gremlins
 
Check the connections and voltage at the diamond shaped junction block by the brake booster. That is the connection between the engine side and the rest of the truck. Since you have 14.2 at the alternator as pointed out above, you have a good alternator. Something is keeping it from the rest of the truck as also pointed out above.
 
That is what I get for watching a football game while writing a reply. 10 minutes and other people posted what I wrote.

Yes, there is a usable link at the end of the power wire running from the big lead on the starter solenoid to the diamond shaped junction block. They do degrade as pointed out.
 
So from memory there are two red wires coming from the back of the fuse box
1 goes to the starter
other goes to the alternator
they both are tied at the bus bar at the junction block by the firewall
I've replaced both of this wires with 10 gague wires, as well as replace the fusible links.
is it possible that I have something reversed?
 
OK. First thing. Where are you getting your ground reading while doing your voltage tests. Engine block, body ground? If you are taking your readings with the ground of your meter, on the engine block, then you are going through the neg. battery cable for your ground. If you move you meter to the body, then you are using the body ground. Your body ground might be bad, which causes a low reading, even if your pos. connections are perfect.
 
I've been using mostly body grounds
to get my readings.
I will go back out later today if the weather allows and check again.
 
Well ad promised I went back out to re test my readings
with the truck off
I got 12.3 at the Battery, alternator stud as well as the junction box at the firewall.
With the truck running I was getting 14.9 at all three locations
I used the battery negative for a ground point and some fancy test light that will read out voltage in place of the old boring light on.
One thing that I discovered is the ground 4 gauge cable from the battery to the rad support was loose.
I guess I have to go back an re check all the connections and even upgrade some. I'm using 4 gauge for all the main pos and negative connections.
It tool a while to unearth the hood since I'm just now recovering from all the snow we got in the Sierras the two pictures are my front yard and patio table. We got 14 inches the first day an a total of 2 feet

20221231_173927.jpg

20221231_173945.jpg
 
MEMO43 said:
Ok here is my dilemma
I have an 85k20 that I swapped L31 engine in
kept the serpentine system. Have added a summit Max efi kit to it.
New Battery AGM, New alternator but yet I'm not charging and my truck will shut off due to low voltage that the EFI requires
I'm running a CS140 alternator from orileys (140 amps)
I've replaced the positive cable from the battery to the starter with 4 gauge wire
same for the ground wire.
From the Fuse box to the alternator is 10 gauge, same for the wire that goes to the junction box as well as the starter.
I'm using the correct adapter for the alternator.
My issue is at the battery with the engine running I get 14.2 same as the power stud at the alternator bit everywhere else I get 12.3 all the way down to 10.2.
I've traced and tested every wire that I could think of and came up empty handed.So before I do the knee jerk reaction or rewire the entire truck

Is anyone running either a CS130 or Cs140 style alternator that is a true 1 wire and if so what is the part number and were did you get it from.
Click to expand...

nobody else has brought this up yet - you mentioned an adapter??? you meant one of these things? there are gm/ac delco part numbers for an adapter that plugs into your wiring harness, and then into your alternator. there are at least 2 types They have one for a truck with an idiot light, and one for a truck with a voltmeter? there will be some kind of diode/resistor combination built into the adapter. they are less than 20 bucks? I had to use one on my 1988 when the big one wire alternator from a cop car came to me and got installed.

-edit- eh... reread everything here, and this adapter seems less likely to be involved as an issue. Im thinking more along the lines of damaged fusible links?

alt.jpg
 
Last edited:
@scouthead
I have two different adapters similar to what you mentioned.
one has the resistor the other does not.
I've also made sure that the only wires connected are the S and L terminal.
I have the S terminal connected to the junction block on the firewall. the S terminal connected to the Brown wire that's intended for the alternator.
My gauhe cluster is the basic voltage gauge without any dummy lights.
I think my issue is one of the 2 red wires coming from the Fuse box at the firewall
one is suppose to go to the alternator the other to the starter.
Although they both are linked at the junction box via fusible links.
So more trouble shooting on my end. As well as go over every mechanical connection I've made.
Can anyone share a picture of how the red wires (alternator and starter) are routed from the back of the fuse panel
I also don't have a positive cable going from the battery to the junction box?
just directly to the starter and the pos lug on the alternator.

The image is some of the wiring I removed from under the hood and cab when I got the truck last summer
although it was parked for 8 years after the original owner passed an his nephews realized it was to much work

20210626_174655.jpg
 
hmmm yeah i dont think im going to have a photo that helps- all my stuff just comes out and goes into taped looms.

Pretty sure my 88 pulls all power from the starter. only positive connections off the battery go to the starter, and the alternator. fusible link right there at the starter... maybe another one on the firewall as well
 
I'll suggest using the truck wiring manual to figure out where they go.

Given the lights work independent of the ignition switch, one probably goes to one fuse panel plug, one goes to another. Really irrelevant where they go into the fuse panel, popping those connectors off (which is generally a mess with the tar sealant they used) you will see where the two red wires are.

Measure voltage on the backs of the fuses (took me a long time to realize you can touch the metal on the back with multimeter probes). There will also be battery 12V terminals on the fuse panel you can test, that would eliminates the ignition switch as a potential culprit.
 
Is the firewall/ fuse box bolt tight? I had that sucker come loose on a truck once.
 
I’ve read that it one of the problems with 1-wire alternators. Essentially the voltage sensor is right at the alternator output (or hidden inside) and so it can’t accommodate big voltage drops in the system.

But sounds like you got something else going on with where the voltage drop is.
 
Check your fuses - I had some really old ones in my 89 and they had a bunch of "toejam" (oxidation) built up on them - so much that it made the fuse terminal holders hot and brittle and eventually they broke off and I had to replace the buss bars. I had a bunch of butched wiring so had to buy a new plug and wire it in myself - I can show you where these go if needed, I am pretty sure the sense wire is at the fuse block which would explain your low voltage.

PO had wired up some wonky switch system to make the gauges work - the fuseholder terminals were completely broken off.
 
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