Piece of cake to add an OD "warning" light to either an SI, SII setup or an SIII-SV set up. I'd suggest using an Ignition lamp, and holder, better yet get a faded one that looks yellow rather than red. Drill a hole in the dash at the upper left of the tach, about 10 O'Clock, not too high and positioned about even between the tach and the Ammeter (or ammeter hole). If you have a spare dash around you can see the actual location as a molding circle in that area on the rear of the dash. .
Then connect one end of the lamp holder to ground and the other end to the right point in the circuit. You really have a choice as to where to connect it depending on what you want the "warning" to tell you. Do you want to know the switch is on , or that the power is now connected to the solenoid. If everything is working fine, you really don't need a light to tell you the OD is engaged. You'll see it on the tach and feel the shift. But the light is handy as follows:
1) For an SII circuit, you could wire it to the switched side of the column switch, that is, the terminal on the switch that only has power when the switch is ON. This way the light will "warn " you that the OD switch is on. Of course if the switch is ON but the tranny is not in 3 or 4 gear the lockout switch on the tranny will not let the OD come on. The nice thing about this is that if your OD got disengaged because you down shifted out of 3/4 , the lit up warning light will remind you that the switch is still ON and as soon as you shift back into 3 or 4 , the OD will re-engage.
2) Or you could wire the light to terminal C2 of the relay, the terminal that provides power to the solenoid when the relay is ON, and the the contacts close. This would "warn" you that power is going to the solenoid, and if you did not feel the OD engage, you would know that the solenoid was probably bad. Or if the light did not come on when you turned on the switch, either the relay or the switch was bad and that was why you did not feel the OD kick in when you flipped the switch.
Tom
