Garmin Forerunner F45 Error Code Fix Guide

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What This Error Means

On a Garmin Forerunner 45, “F45” is a generic system fault / firmware crash code.

In plain English: the watch software has crashed, so it either will not boot, keeps rebooting, or freezes on the Garmin logo, usually after charging or an update.

Official Fix

Start here. This is basically Garmin’s script, just without the hold music.

  • 1. Force a soft reset.
    • Hold the Light / Power button for about 15–20 seconds until the screen goes completely black.
    • Wait 5 seconds.
    • Tap the Light / Power button once to power it back on.
    • If it boots normally and F45 is gone, you are done.
  • 2. Give it a proper charge.
    • Clip the charging cable on firmly. Make sure the pins line up and it is not sitting crooked.
    • Plug into a solid 5 V USB wall charger, not a TV, car port, or cheap hub.
    • Leave it on charge for at least 30–60 minutes, even if the screen looks dead.
    • After that, try a short press of the Light / Power button to turn it on.
  • 3. Update firmware with Garmin Express.
    • On a Windows or Mac computer, install Garmin Express if you do not have it already.
    • Connect the Forerunner 45 with the original (or known-good) charging/data cable.
    • Let Express detect the watch. If it offers software or firmware updates, install them.
    • When it finishes, disconnect safely and reboot the watch.
  • 4. Factory reset (only if it will reach the menus).
    • On the watch, go to: Settings > System > Reset.
    • Select the option that erases data and settings (wording varies by software version).
    • Confirm. The watch will restart and rebuild its system files.
    • Pair it again with Garmin Connect on your phone and set it up fresh.
  • 5. Contact Garmin support if F45 will not clear.
    • If the watch still throws F45 or will not boot after reset and firmware update, you are likely looking at flash memory or main board trouble.
    • Check warranty status. If it is still covered, push for a repair or replacement. Even just out of warranty, Garmin will sometimes offer a discounted swap.

The Technician’s Trick

What the manual does not say, but working techs actually do on stubborn F45 units.

  • 1. Clean the charging contacts hard, not gently.
    • Power the watch off if possible.
    • Use a cotton swab or soft toothbrush with 90%+ isopropyl alcohol.
    • Scrub the four metal contacts on the back of the watch until they shine.
    • Scrub the metal pins inside the charger clip too.
    • Let everything dry completely, reconnect, and charge again.
    • Reason: dirty or oxidized contacts cause flaky power, which is a classic trigger for firmware crashes and F45.
  • 2. Ditch weak USB ports.
    • Avoid TV ports, car ports, cheap hubs, and front-panel PC ports.
    • Use a rear USB port on a desktop, a main port on a laptop, or a decent 5 V wall brick.
    • Unstable or low-current USB power can make the watch crash mid-sync or mid-update and land in F45.
  • 3. Force a clean handshake with Garmin Express.
    • Connect the watch to the computer and open Garmin Express.
    • If the Forerunner 45 is already listed, remove that device entry.
    • Close Express completely.
    • Wait 15–20 seconds with the watch still plugged into USB so the computer mounts it cleanly.
    • Reopen Garmin Express and add the watch again as a new device.
    • Let Express push a full sync and any available software again. This often fixes corrupt system files that keep re-triggering F45.
  • 4. Let the battery fully die, then revive it. (Last DIY move before replacement)
    • Unplug the charger and leave the watch alone 24–48 hours until it is totally dead and will not light up at all.
    • Then plug it into a solid wall charger and leave it charging for at least an hour without pressing any buttons.
    • After that hour, do a soft reset: hold Light / Power for 15–20 seconds, release, then short press once to power up.
    • A full power cycle like this can clear a stubborn crash loop that normal resets do not touch.

Is It Worth Fixing? (The Financial Verdict)

  • ✅ Fix: F45 showed up once or a few times, the watch is under about 3 years old, screen and battery are fine, and a reset/firmware reload brings it back. Cost: your time and maybe a new cable.
  • ⚠️ Debatable: Repeated F45 on a 3–5 year old Forerunner 45 that is out of warranty but otherwise clean and not abused. Worth asking Garmin about a discounted refurb swap, but do not dump money into third-party board repairs.
  • ❌ Replace: Constant F45 plus other issues like weak battery, cracked screen, or obvious water damage, and Garmin wants a fee close to a newer model’s price. Put that cash toward a new watch instead.

Parts You Might Need

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See also

If you are chasing other error codes around the house, these might help: