Turn signals suddenly stopped working. Is there a fuse to look for? Where do I start to trouble shoot the problem? {John, KY, USA - 2004 Suzuki GS500F}
A quick review of the schematics for your GS500F show that the bike has a
turn signal relay assembly, Suzuki part number 38610C01D10J000. It should cost approximately $20 at a dealer or online retailer like Bike Bandit (click the banner below).

The GS500F appears to have only one
fuse, located in the starting motor relay assembly. This is not very likely to be causing your trouble.
This brings us to our last suspect, the turn signal
bulbs themselves. Motorcycles can be very temperamental when it comes to electronics. They dislike automotive light bulbs. For their sensitive electronics to function properly you should use bulbs designed for bikes and always match them. If the bulbs are even slightly different, it can throw off the relay. The parts fiche shows 12 volt, 21 watt turn signal bulbs, Suzuki part number 09471-12045.
If none of these turns out to be causing your turn signal problem you could have a broken wire, a dirty switch or corrosion in the socket. You can test for broken wires with any multi-meter, use an electrical contact cleaner on your handlebar switch and clean your sockets with a dry wire brush.