So, attached is a pic of several different switches from my bus (a B
...These are Eaton switches, but I think the Carling variety are similar in operation.
The switch on the left has 2 different "on" circuits, and two bulbs; the second one has online "on" circuit and one bulb; third switch was from a rear heater control, so has a "on-off-on" configuration and only one bulb; the last switch was the bus warning light start, so it is. only an intermittent switch, again with one bulb.
As I have annotated, the top row of terminals is for the light that would presumably illuminate the switch when you turn on your headlights. For the first switch, you could also use this bulb to indicate the load that is running when the switch is in the upper position.
The middle row of terminals is for the 12V input to the switch - usually associated with a circuit that is active only when the ignition is on (bus running). The terminals on either side of the middle row are for the 12V supply from the switch to the load it serves. The bottom row of prongs on the first switch serves the 2nd bulb.
On the first two switches, you will note that there are both left and right terminals in the middle - these are separate circuits (left/right) and could in theory be used to drive 2 separate loads...For example, on my bus, I rewired the overhead warning lights to be high turn signals and brake lights, but also used switches to be able to activate or deactivate this feature...So on the brake lights, I use the left input/output to actually activate this, and I will eventually use the right input/output to feed fog lights...the second (lower) switch bulb on that particular switch will illuminate when the feature is activated. (On the T/S switch, the lower switch bulb just flashes when the high turn signal flashes.)
As far as using jumpers, basically all you would need them for is to: (1) tie together two negative (ground) terminals on a switch (if so equipped), (2) tie together the positive inputs (middle terminals), or (3) tie the positive output terminal to a positive light input to have the light illuminate when the switch is "on".
Note that it is not a foregone conclusion that all of the terminals on the switch will have a wire going to it...depends on what type of switch and the needed service. Hope this helps a bit - can also see the following link for some specific tech references for Carling:
https://www.carlingtech.com/sites/default/files/documents/S-Series_Details_%26_COS_112712.pdf
