I need help understanding wiring on oil and amp lights. The oil light has white/ red wire and green/black wire I know the white/red wire goes to sender. Does the green/black wire go there also or does it go to a ground? I have totally lost track of wiring for amp indicator light wiring. This is for a 1966 ford custom cab with both amp& oil gauges and oil & amp indicator lights. Any help would be appreciated. Thanks Jerry

 

A wiring diagram can be had for around $7. Do a search. There are some posts with wiring diagrams attached.

 

Been there done that I have several wiring diagrams all related to my year. There is no wiring diagram for oil amp indicator light. Gauges are covered but nothing on indicator lights. Thanks for the reply Jerry

 

I looked at my unmolested 1966 F100 custom cab and the ALT light had a black w/green stripe and a yellow w/black stripe wire coming from it to a harness. The Oil light had a white w/red stripe and a black w/green stripe coming from it to a different harness. Thats all I can tell you.

 

I checked my '66 wiring diagrams and found the same things you did OldSchool.

I can offer this with regard to the oil light. The white/red wire runs from the light to the sending unit, and the sending unit is a pressure switch which closes under low pressure conditions. Given that, the black/green wire would have to be powered with the key in the "on" position. This would allow the oil to come on when the ignition switch is turned on, and for the light to go off but remain powered with the engine running, since the engine oil pressure is holding the switch open.

Now for the alt light. I am going by old memories, and a bit of deductive reasoning, based on more than 50 years messing with older Fords. Since Ford typically doesn't mix wire colors, the black/green should be key on hot, like the oil gauge. The yellow/black would most likely run to the voltage regulator, perhaps the I terminal?? With the key on and engine not running the alt light is powered and grounded through the I terminal. With the engine running, and the alternator charging, the contacts the I terminal is connected to open, interrupting the path to ground, so the alt light goes off. When the I terminal contacts close, due to low voltage or loss of charge, the alt light comes back on.
I have also seen Ford use opposing voltages to control lights, and this may be how the alt light is controlled through the regulator.
Regardless I am pretty certain the yellow/black runs from the alt light to the I terminal of the regulator.

Hopefully someone a bit more schooled in the '66 wiring can confirm the alt light question.

Goodluck. ope this helps.