i have a 2013 GSA and the OEM fog lights do not illuminate. The bulbs are good, both fuses (left and right) are good and the green light on the toggle switch DOES light up when selected on. Any help would be great. Just give me some direction please.....
This is very likely a relay issue. The lights are probably connected directly to the battery through the relay. The green toggle switch will probably control the relay's enable. So depending upon how you've got it all wired up, here are some pointers:
The relay should have a 12V coil. The coil requires that 12 volts be supplied to one end and ground to the other end. Make sure that you connect it with the right polarity otherwise the snubber diode (if included) will short your circuit to ground. When you energize your coil, you should hear it engage with a 'click' sound. This truly depends on if your relay is electro-mechanical but in most cases this will be the type. I prefer MOSFETs and you'll never hear them click. If the coil clicks when energized and clicks again when released, then your relay coil is good.
Next check the contacts on the other side of the relay. One should feed directly from the battery and the other will go through your lights to ground. Check for voltage on both sides of the relay contacts with the switch disabled. You should have 12 volts on at least one side. If you have 12 volts on both sides while the switch is disabled then there may be a different problem. Now switch your switch to the ON position and check for voltage again. If you still have voltage on the original side and you have voltage on the other side then your relay is probably good. This, of course, is assuming that the relay is on the supply side of the lights and not the ground side of the lights. If the relay is on the ground side of the lights then you will see voltage on one side when the switch is OFF and ground or 0 volts on both sides when the switch is ON.
This is assuming that you have a relay installed. There is the possibility that your lights are tied directly to the switch and a relay is not being used. If that is the case, check to make sure that you have 12 volts on one side of your switch while it is in the OFF position and 0 volts on the other side. Then switch it on and check for 12 volts on both sides. If the switch is good then you need to start tracing wires.