Key switch wiring for Diesel with heater, and safety switch.

[Destroked 450]

Yes, that is how it usually works but when you crank, you power the wire to the oil pressure switch, which is closed initially. Therefore, you should get a short to ground.

Perhaps there is a resistor in the oil pressure switch. I do not understand why the wires are connected this way.

The oil pressure switch provides the ground to turn the light on, once the engine makes oil pressure the switch opens, no ground no light

 

[Hacke]

The oil pressure switch provides the ground to turn the light on, once the engine makes oil pressure the switch opens, no ground no light

Yes, that is how it usually works. According to the diagram, there will be a short to ground through the oil pressure switch, when you crank.

Apart from that, the oil warning light will always stay on when the key switch is in on-position, since the bulb will be grounded through the solenoid coils.

The diagram has to be wrong, it would be interesting to see how the connectors on the 3600 are wired in reality.

Below is the equivalent connectors from a diagram for a 3610 gasoline tractor. That will give a normal function. Both diagrams are from Ford documents.

 

[Destroked 450]

My book shows the same diagrams and I believe there could be a mistake made, not the first one I’ve found in the later manuals

My understanding is you’re trying to wire up the ignition switch and the original harness hasn’t been butchered
So here the switch terminal numbers and wire colors for that terminal
(1) one red wire and one red with gray stripe
(2) one brown wire with yellow stripe
(3) one brown wire with red stripe
(4) one brown wire
Does this match the wire colors you have