Hey guys,

I was just outside testing out the lights on my truck, you know, seeing what it looks like from the front, rear, side etc. I had the 4 ways on and I noticed that the license plate lights pulse slightly with the flashing of the tail lights. They dim slightly every time the tail lights flash on bright. I then tried the turn signals. If I have one of the turn signals flashing, say the left one, the right tail light and the license plate lights have a slight pulsing.

The front lights are solid and don't do this so it's something that is affecting only the rear lights. I'm just wondering if this is "normal". It's not a big deal I suppose, but its just something I've noticed as I'm checking over the truck in detail. I found a thread on another site where someone else had noticed this too. I'm curious if anyone else's truck also does this.

http://www.fordtough.ca/forums/showthread.php?t=7667

 

bump...

Anyone? I just would like to know if anyone else's rear lights do this. I can take it to the dealer but if this is normal I won't bother.

Thanks!

 

I'll check mine later today. I've never noticed it though.

 

Sounds like they're running power to the back of the truck with awfully small guage wiring. Sure it's only a couple amps but it's also only 12 V and a long ways from power--as the wire routes.

 

Sorry to bump this again, but I'd really like to hear from others if your truck is doing the same thing with the rear lights.

I checked the ground wire and it seems securely attached to the driver side frame rail under the bed (right above the spare tire). Of course, its on the top of the rail so I can't really see it or get access to it.

I may take it to the dealer but just want to see if others have this issue too. I hope this isn't the sign of electrical issues because those can be a complete PIA to deal with.

If anyone has the time, just throw your 4 way flashers on and your parking lights and check your license plate lights for a pulse.

Many thanks!

 

Mine do not pulse.....or if they do it is not noticeable.

 

Well, the dealer said that this is a normal condition for the vehicle. They looked at my truck today and then checked 3 other trucks on the lot and they all do this. Not sure it supposed to do it, but it sounds like its common. They also said they never had anyone point that out before. LOL.

 

Wonder why?

Not important

 

To some!

 

Mine does not seem to have this issue.

 

Even though the dealer told me the other trucks on the lot do it, I'm still going to try and figure it out. It just looks crappy.

I'm going to try pulling the fuses that power the trailer connector and see if it makes a difference. My guess is that there is a bad part or a certain production run that is causing this minor issue.

 

Okay, so I pulled the harness connector off of the trailer light hookup and it made no difference.

When I have more time, I'll check the white ground wire that is screwed to the top of the driver side frame above the spare tire. That is where the rear lights are grounded from what I can see. I might try temporarily grounding it to a different part of the chassis to see if that fixes the problem. Since the front lights are fine, it must be something going on at the rear of the truck.

For anyone that is familiar with vehicle wiring, can I run a long wire from the white ground wire at the back of the truck all the way to the negative post on the battery? Is this the best way to check for a bad ground?

There is obviously some reason that the lights are dimming and I'd like to try and figure it out if I can.

 

Here are 2 very short videos of what my lights are doing. This just doesn't look right to me, but other F150s do this from what I've seen. Very strange.


First, with the 4 way flashers on…





Now, just the left turn signal on. Notice the right tail light pulsing. This also happens the opposite way around too…

 

My truck does the same thing that yours does, I just checked. I also tried while the truck was running...same thing.

The front blinkers have no issues and neither do the flashers on the side mirrors.

Perhaps its normal but can only be noticed at night? Whatever the case, I'm not too concerned about it, but I would interested to know what the cause is.

 

Been in an house with an older electrical service and noticed when the A/C kicks on how the lights dim? Same thing. There is a load on the circuit when the light flashes which causes a temporary drop in voltage which causes the other lights to dim. Not a big deal.