Vortec (LS) alternator and charge light help (2 Viewers)

[RredFJ40]

So, I’ve searched and tried the fixes that I’ve found posted so now coming for help and clarification.

82 FJ60 getting a 99 LM7. Alt is a cs144 4 pin connector but the stock harness has a single brown wire to the L terminal.

Bear in mind that I think my stock alt wiring was jacked!

Yellow from alt plug (turned to white, supposed to be y-w?) I hooked to the S terminal. The b-y wire from the alt was hacked up but I think I found it. It has continuity with the b-y on the charge light relay. I spliced it into the brown wire on the cs144 plug. Running, it’s getting 15v, nothing at the s terminal and the charge light stays on. What am I doing wrong?

Maybe someone can explain this circuit to me?

 

[RredFJ40]

Also, I swapped in an fj62 combo gauge, everything should still work correctly, right?

Anybody got a better wiring diagram than the Haynes manual?

 

[FJ60Cam]

Not sure if this helps, here’s how I hooked up my stock FJ60 wires. I was using a DR44G, so you’ll have to adjust for your inputs ...

Post #882

I think there are some links to CS144 alternators in there if this info isn’t enough.

 

[Well Sorted]

I'd have to go back and dig out the FSM diagram to figure out exactly why I did it this way but on mine I have the yellow wire spliced into the brown wire on the L terminal. I don't have any other wires connected in the 4-pin plug. The main charge wire goes to the battery and the factory power distribution is powered at the + terminal through the normal fusible link setup.

Charge light works fine, 14.4 at the battery when running.

 

[RredFJ40]

I'd have to go back and dig out the FSM diagram to figure out exactly why I did it this way but on mine I have the yellow wire spliced into the brown wire on the L terminal. I don't have any other wires connected in the 4-pin plug. The main charge wire goes to the battery and the factory power distribution is powered at the + terminal through the normal fusible link setup.

Charge light works fine, 14.4 at the battery when running.

You can see why I asked for help, so many folks doing different things.
I’ll give this a whirl first since you had a single wire Chevy alt? What did you do with the b-y wire from the fj60 alt?

 

[RredFJ40]

Btw, thank you both!

 

[Shes Mad]

I have the same motor (LM7) in my 87. I can check it if you need when I get it back from paint in a week or so.

 

[RredFJ40]

So a small update, I’m not done troubleshooting yet but for posterity here is some info:

Though the plug on the back of combo gauge is the same; my 82 FJ60 cluster and the 89 FJ62 cluster are wired differently, in particular the charge light and high beam indicator are not correct. I hit the high beam switch and the charge light went out

Anyway, swap the gauges back and I have no charge light at all

The truck has other wiring issues as the yellow wire off the L lead is spliced into some unknown white wire ~12 gauge, that does not have continuity with the charge light relay.

Everything worked as advertised before the swap, I just don’t know why!