Most likely scenario: The 2005 F-350 likely uses a Body Control Module (BCM) which integrates the flasher function. There's no separate, easily accessible flasher relay like in older vehicles. Any issues with the turn signals will require diagnostic testing by a mechanic or using a scan tool to identify the problem within the BCM or related wiring.
Less likely, but possible: In some very rare cases (depending on trim level or specific options), a traditional flasher relay *might* be found in the under-dash fuse box. However, this is not the standard configuration for this year and model.
In short: Don't waste time searching for a standalone flasher relay. If your turn signals aren't working correctly, you should consult a repair manual specific to your 2005 Ford F-350 or have it professionally diagnosed. A faulty BCM is a far more likely culprit than a separate failed flasher relay in this case.
