Alternator has me frazzled

[ol Curt]

I recently noticed my GEN light staying on all the time when my truck was running. I reasoned it would be a good time to just replace the alternator with an internally regulated one. I followed the instruction in the FAQ section. I have 14 volts at the battery when the truck is idling, but the light stays on. I reversed the wires just to be sure...light stays on, but 12 volts at battery.

I'm guessing I had the wiring part right. What will cause the GEN light to stay on?

This is on a 250 six in a 66 C10 with warning lights rather than gauges.

[ol Curt]

As i continue my quest, it has been suggested that there is probably a short between the alternator and the gen light. I am considering running a new wire from the firewall harness back to the new instrument cluster(light) harness as those harnesses are both new. I am puzzled what to do with the brown/white wire from the ignition. The diagram here shows it is a resistance wire. Would i need to run a special wire for that, or is it just a plain 24 ga. wire as indicated on the wiring diagram?

[ol Curt]

Here is the diagram showing the circuit. the tan wire is the brown w\white stripe indicated as the resistance wire above.

[BTCHN 1963]

Curt,
You can run a standar wire, but you need to have a piece of resistance wire in there. You can pick up the resistance wire up from most autoparts stores. With the resistance wire in there it will melt before the whole wire does and it can be replaced. I dont remember if the standard wire needs to be a larger guage or not. I have personally run a standard 10 gage to a points distributor before and for the ten years that I had it, it never gave me any problems. You could also call your local auto rewiring shop and ask their advice.
Rob

[BigJackDaddy]

Write-up here

[62gmc910]

Originally Posted by BigJackDaddy

Write-up here

bottom diagram is almost right , blue wire needs to run thru light to Ign switch acc terminal Also if you run high draw electical loads they need to be run thru a fused source at the battery/ horn relay junction because the trucks wiring is not designed for much load some alts won't field (light out)until higher rpm (1500 ish on fire up)

[fixit-p]

Your problem is an alternate ground path in the gen light circuit,
The diagram you posted in post 2 is an isolated circuit the resistor is not needed with a gen light (gen light provides resistance) but Delco does recommend wiring one parallel with the gen light (notice common connections at reg and ign sw.) for redundancy (if gen light burns out alt still works).

The gen light is supposed to get power from the ign sw. with engine off power flows through the alt field windings to ground (light goes on) once engine is started the field is excited and no longer allows current to flow to ground (positive voltage present) in fact once you have positive voltage on both sides of the gen light it goes out (no path to ground) the SI series alt's will cause the light to glow if voltage drops on either side of the gen light (not so with the CS series)

Look at the diagram you posted in post #3 you'll notice a common connection with the oil and both temp lights (generator circuit) there is the problem you need to isolate the gen light circuit use the diagram in post 2 the others further down are incorrect. The conversion you followed was fro external reg to internal but I think you went from generator to internal reg alt. HTH

[ol Curt]

Got it!
Working like a champ!