I noticed the other day after glancing at the taillights on my 2010 FX4 that when one of my blinkers is on (right or left), the opposite side taillight is making a faint blink with the other sides blinker?? It is really faint like you could only notice it if you look at it close but now that I have noticed it I am kind of bothered by it because I know that it is there. It only does it when the running lights are on to the taillights and then works fine when the headlights are off since there is no running lights, but it seems like the one is pulling power from the other one somehow when the running lights are on and I am just not sure what I can check to try and fix the problem or if that is just the way it is on our trucks that it is pulling so much power from the taillights and other lights that it would cause what I have described??? I am no electrician but have some basic knowledge of wiring so any help would be appreciated or if anyone can check their truck to see if it does it because I am thinking that it shouldn't be doing this or I have never noticed it until now. I have some LED taillights from Recon on the way but want to have this fixed before I install them.

Are there any relays or fuses to check for the running lights? They work fine on the trailer plug and are obviously on in the taillights so I wouldn't think a fuse is blown but didn't know if there is a relay to check or what exactly the relay does?

 

Should not do that sounds like a bad ground looping back.

 

That is one of my guesses but not sure where the grounds are and why it would have all the sudden done it.

 

I'd start by checking the most likely point of concern, the rear bulbs and sockets. Pull them and check to see if you have any corrosion or bad contacts. My guess is you will.

 

Yep mine does it. Do a search and you will see this has been brought up before.

John

 

I will check the bulbs and sockets on the taillights as there may be some moisture but they should be sealed to where nothing should get in there.

What do I search for to find this info?

I also wanted to add that I just checked it again a few hours ago and my license plate lights flicker as well!!

 

i dont think it would be the bulb there should be 3 wires to each bulb 1)ground 2)all time power 3)you can say a relay switch wire. the light wont come on until the relay wire gets a signal then the light will come on powered from the all time power until the relay wire tells it not to. if your light was just flickering (such as all time driving light) it could be caused by a bad connection on the bulb or ground, but in your case you cant light up what doesnt have power going to it. your problem could be from your relay switch, turn signal switch, or poor wiring from the power signal as well. i have an electronics degree but im not a mechanic, i hope this might help.
-zack

 

it may also have something to do with the hazard light setup, i dont know for sure. keep us updated.

 

So digbyz what do you think I should check or test on the truck and how do I go about doing it? I think you might be able to help me.

I checked all of the bulbs and sockets and they all seem to be fine with no corrosion of any type. I am thinking of taking it to the dealership but would rather try and diagnose it myself if I can. I unplugged the trailer tow harness and that didn't change anything so I eliminated that.

Are the license plates on the same ground as the taillights/running lights I am guessing?

Thanks for the info so far guys and hopefully I can figure out the problem soon.

 

I think it is normal and just from the drop in current due to the flashing. The license plate lights also faintly blink. If you search you will see several others have commented about it.

BTW if it was a bad ground, wouldn't they flicker all of the time or also when the brakes are applied?

 

Pig9r, Does your truck do this?

 

Yep and the headlights dim when the e-fans kick on or roll a window up or down. Not really concerned with either.

Here's an old thread on the issue:

https://www.f150online.com/forums/20...-question.html

Hope this doesn't ruin your weekend but have you felt the wiper motor torque through the brake pedal yet?

 

Here you on the Pig. Even on the 04-08 models you do too.

 

as far as i know the taillight / blinker lights- combo, not just a running light. those that have three wires. are
ground, parking, turn.

i never noticed this issue on my 09. until i installed LEDS up front. the switchbacks from v-leds.com

within their bulbs at least- the parking and turn are internally connected, when i did not have at least the parking lights on. 1.5v would back feed to all other lights. front side markers. rear tailights. ect.

they wouuld faintly flash. before i had regular silver star parking/turns up front so the filliment ate up that 1.5v with no noticable light.

when you put in leds. or if you are going all LED. you will need to install diodes on all four rear taillights, i installed them on the front park/turn as well.

to fix the hyper flash. you can either live with it . which is what i did. or install resistors. with all led. v-leds reccomeneds 3watt.

they will get HOT HOT HOT.

the flash is faster . but there is still a noticable on .. off.. on. so i dont think its unsafe. and i have never been pulled over .

where are you ordering from? for the leds.
they have a few troubleshooting pages as well. wihich covers this. or you can also email them.

 

Thanks Pig9r for posting that link to the thread I started on this a while ago.

Well, I've observed that every single late model F150 (this gen and previous gen) seem to do this little light show. So it seems to be "normal" for these trucks.

Here are the videos I took of my truck...