2021 F250 Lariat 45,000 miles. The right-hand turn signal started blinking fast. I checked all the light bulbs, and they are all working properly. What else can it be? It's beginning to drive me crazy! Thanks for your help!

 

Change any bulbs for LED?
Usually indicates a bulb out or one is not pulling as many amps as normal.

 

Everything is OEM. I read that maybe one of the bulbs is failing, but everything looks fine, nothing obvious.

 

Could be a dual filament bulb and one of the filaments is burnt. Like a brake bulb / turn signal combo and one is burnt, or running light / blinker and one is burnt.

 

Yeah I posted this before but believe me or not I had an intermittently little flicker of a bulb on my rear turn signal/brake bulb. Halogen.

Literally had people watch it run through all its light sequences several times trying to see if there was any faults.

It wasnt until someone was backing it in and i saw the rear bulb briefly dim/flicker when they hit the brake or door lock or something. Was a long time ago. It went on for months and months. Was a few dollars to fix.

But yeah, get some bulbs from the parts store and change the taillights. Hopefully that fixes it, fixed mine.

 

My thought exactly.

 

Had the same thing happen on my ’22. Burned out bulb in a taillight was the cause.

 

Assuming you have incandescent lighting as others have suggested it is probably one of the dual filament bulbs. It was the top right on mine. It can be hard to spot, many have sworn they were all working. Easy to fix.

Hopefully that’s all it is. If you haven’t had any other issues and it started suddenly it probably is.

 

If it is a bulb in the taillight, watch a video on how to remove the taillight so you don’t break the tabs.

 

i had this issue as well. inside left turn signal flashing like crazy and it turns out one of the halogen brake light bulbs was partially burned out.

 

They make plug & play LEDs now. You should be able to get a set for somewhere around $60, and get bulbs the same color as the housing (red bulbs for red housing, clear for clear, and amber for amber). I made this change when my halogens started dying, doing the same thing yours is doing. LED is the way to go. And I'm only talking about taillights. LEDs in halogen housings up front are just a nightmare for oncoming traffic.