No reverse light!

My 83 cabby doesn't want to turn on the reverse lights!! The bulbs are ok! Where shoud I start?

Thank you! 

Unplug the plug off the switch in the gearbox. Get a bit of wire and bridge the plug out and see if the come on. If they do the switch is porb gone. If they dont come on check the fuse if there is one

So… if I connect these two wires, I have reverse lights!! What now? 

Most likly you need a new switch.

Solved!!