idot light on but charging system is OK?

This is in an 84 Ranger, 2.8L, automatic, no air, 2wd.
I replaced the alternator and regulator and the charging system is working fine... but the red idiot light is on.
Trust me the charging system IS working, only thing is that red light.
I'm thinking there's a diode somewhere in the circuit involving the idoit light.
Anyone know what's going on? How to restore the idoit light to it's correct function?
Thanks, Doug in western NC
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There a number of possibilities. There is no diode. The charging system is still not correct. The 500 ohm resister that is in parallel to the bulb is open. The wire between the bulb and the regulator is shorted to ground...........

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