Charging light wire as relay trigger too?

[bhap]

I am converting to a CS130 alternator with indicator lights on dash, not gauges. Am I able to splice into the 20 ga "L" terminal wire and use it as a trigger for a switched ignition on relay at the same time? I think this should work, but don't want to mess up the way the dash light works. I could run a separate wire, but this would be easier.

[VetteVet]

I suspect that the relay coil would provide a path to ground for the L wire and the alternator would not work. Also the light would not work. It would remain on all the time.
The L wire is the exciter wire for the alternator and it also varies the current going into the alternator armature to compensate for the loads on the truck circuits.
I don't recommend tying into the charging or ignition wires. There are better ways to wire relays. I'm not sure I understand what you want to do here, you have to turn on the ignition switch to get power to the L wire before you can power a relay to turn on the ignition switch.

[bhap]

I thought there might be an issue with the wire finding ground through the relay. Maybe a diode? The relay would be for an ignition switched accessory, not to supply main power to the cab. I was trying to stay within the stock wiring connection through the firewall.. I'll find somewhere else to run an ignition switched wire to trigger the relay.

Thanks for your help VetteVet!