left turn signal flashing fast

If the turn signal relay is easy to get to, change it and see if that solves the problem. They're not expensive. If that doesn't work you will have to dig deeper for things like bad ground, or insufficient voltage. The net probably have videos of how to check and where.

Apparently, there is no relay on the 2012 and up F-150s. There is a module called the BCM that houses the function of the signal light. I think you are right about a bad ground. Not sure why the right signal works though.

Did you find the fix? Mine is doing this also ):

2014 does this and bulbs are fine

my 2014 f150xlt does same thing anyone find the fix for the problem???? diy jimw

My 2018 does same thing

I'm having the same issue - 2014 Limited F150

Save yourself some time and money and headache - I had the very same problem and read all the responses that I didn't think were relevant. You should know - there are two turn signal bulbs on the left rear, and two turn signal bulbs on the right rear. Do yourself a favor and change both on the side at the same time. I can't believe nobody posted this earlier on a 9 yr old thread.

2014 F150 Lariat 501A pkg. 67k miles. Having same issue but will add some details. My issue like the others here is also only the left turn signal flashing fast but it will act up for a day and then go back to working normal. The last couple of days it has been flashing fast then tonight it started flashing normal. Also my gas mileage went from 20 MPG down to 14 MPG and tonight when I notice the signal work I noticed my MPG went back to 20 MPG. I thought it needed spark plugs and the sensors cleaned but not sure what to think now. This thread shows that it's the left signal always flashing fast so what's going on?

2012 doing same...left side.... Does the front side marker bulb blink? It looks dim when running lights and/or headlights are on,of course so does the right side but the right side blinker is fine. Wondering if side marker causes blinker to go fast if it’s on it’s way out? However I will check to make sure both rear bulbs on left are blinking.

12 gen has a problem with bad turn signal sockets in the tail lights.

My 2012 had the same problem. It was a bad socket. It's all controlled by the smart junction box which has to be reset. Be careful that can only be reset 5 times then it has be replaced a d it is real expensive

Ps it's doing it again. not sure what it is this time

Same thing on my 2014. Read through the thread and m wondering about a bad socket or connection at the light. The top rear blinker was steady and should be blinking. Gave it the Fonzy back hand and sure enough it is back to working. Have to get in there and see what is going on.

The guy who answered about the two bulbs in the back was the problem with mine there's one on top one on bottom for the blinker I changed the bottom blinker works fine. Thank you sir.

Left turn signals hyper blnking. Replaced front and rear bulbs, they were woking just on the r side. Is there a relay or flasher and if so where, Need help desperately. 2 tickets already

Read on here to remedy this problem change both of the bulbs (there are two in the rear light) It worked. Now they are blinking at the correct speed. Thanks

I have an 09 F150. I had the same problem on the left side. To make things worse it was intermittent. Someone posted earlier to replace both bulbs. I did that, problem solved!

2011 F150 left turn signal flashes fast. both rear bulbs flash when turning replace both bulbs and that will solve the problem.

Same issue with left side fast flash. Have after market led taillights so it wouldn’t be a bad OEM socket problem. So what else besides bulbs?

replaced all 4 rear bulbs,,, Working fine

Guru94c196.. you could fix the hyperflash by changing the settings using forscan. I'm looking for the correct module lines to change for my car. Let me know if you find something

GuruNN374 was correct on this problem for me. I have a 2013 and I tried everything prior to doing what he said about changing the two rear bulbs. It fixed the problem.

How do you change the rear bulbs? I have a 150 lariat! Thanks

2014 F-150 FX-4. I had the same left turn signal issue. It was blinking fast but working. There are in fact two blinker bulbs. One upper and one lower with the break light/reverse light in the middle. I replaced BOTH upper and lower blinker bulbs and it fixed the issue. The taillight comes out super easy. Remove the two 8mm screws inside the tailgate that hold the taillight assembly and pull it straight back.

I just got no power on right side left side works good

I can only speak for the 2010 F150xlt. The tail lights both top and bottom flash. Check to see if both top and bottom lights flash. If one is out the blinker will flash rapidly. Replace the bulb not flashing.

does fast left flasher have anything to do with tail lights not working?

I have a 2014 Ford F-150 and took the earlier advice to switch out both left rear bulbs. It fixed the issue. Thanks for the help!