With anything electrical, go step by step with your multimeter. Start at the battery and trace the wires to see where the break is. Follow the circuit diagram for your year and model, and trace along the circuit for the fog lights. It's very difficult to diagnose electrical issues without having the vehicle in front of you and available for test.
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk