What is the quarter inch diameter light in the Ford model 1710 4X4 dashboard

[airbiscuit]

The wiring diagram shows it as a charging light. You don't have an ammeter gauge so that would be logical.

 

[sod buster]

Thanks to all for your help. Definitely appears to be an add-on, not factory.

 

[RickB]

The wiring diagram shows it as a charging light. You don't have an ammeter gauge so that would be logical.

Charge lamp and low oil pressure indicator are integrated with the tach/hour meter.

 

[CoyPatton]

Since you have that heat coil (‘cold start aid’) on the left side of your dash u less it was added to that circuit as a user add on, I would doubt it to be for the glow plug circuit.
Most 3 wire bulbs for a warning light will have a ground wires (the bulb will be in the circuit wire and use 2 contacts and the 3 a ground) so if it was added to the glow plug, the ground would allow a completed path for the bulb to light, the power input line coming from a timer relay (if equipped) and then the last wire to the glow plugs to deliver the power to them.
You need to chase those 2 wires present to figure out where they go!
It could be for any type of lite feedback.