Both of my front sidemarker signals do not work. All of the other signal bulbs work though. When I turn on the lights, the sidemarkers light up but still doesn't respond to my signaling. The signals still flash at a normal rate. Are the sidemarker lights bad or is there something else wrong with it?

 

The lamps are dual filiment type.
If they work as markers then either one element is burned out or the feed to them is open.
To test the bulbs, operate the 4 way flash. If they work then, the bulbs are good. The 4 ways supply power thru a different set of contacts.
If the rear tails work as regular turn signals, the turn switch should be good.
The probable... has to show up in this testing.

 

I checked with the hazard and they don't light up either. I replaced the bulbs--still no go. So something else other than the bulb is causing this then.

 

If the parking lamp circuit still works, and the front signal ( the brighter element ) is not, I would think the MFS is giving you a problem.

If you want to take a look at the MFS connector under the steering wheel cover, for loose / worn pins or a cracked hood, might be worth a try.

Here is thread on MFS testing, but this was with high beams, not the turn signal part of the MFS ( different circuits in the MFS , included test chart for turn signals.)

https://www.f150online.com/forums/sh...d.php?t=278410

There seems to be some more common ( not common as in all the time ) problems with the MFS connector coming loose, or the pins being discolored or slightly worn / bent causing problems.

The output of the 4-way and the turn signal are both from the MFS. The 4-Way button just connects both the L & R sides at the same time, where the turn signals are L or R.

Let us know what you think or find.

 

You know what? I think I might be retarded. Maybe the sidemarkers aren't supposed to flash on the new models--only the two middle front bulbs.

 

The corner lights on t'04+ MY trucks do not flash.

Those are 194 bulbs, single elements.

This is the square-ish yellow reflector face you see when looking directly from the side of the truck.

There is a separate 3156 or 3157 type bulb in the round on the face of the hedlamp. This is normally a yellow bulb that people sometimes switch to the SilverStar one, so it look clear when off, and yellow when on.

Is this what you are asking about ?

 

I was talking about the 194 bulb. I looked at it and saw it only had 1 filament then I realized I wasn't thinking correctly. I was so used to having my other cars flash the corners that I thought something was wrong when I didn't see this car flash those. It would be safer if they do flash though. Oh well.

 

I added side marker/flash extra lights because when a car or truck gets at just the right position coming along side, they cannot see any signal lites front or rear on the truck.
If you are going to make a lane change or turn, they will miss the signal especially when towing and if the driver doesn't see them coming quick enough it gives the other driver a chance to drop back.
My lites flash alternate with the same side front lights.
I made custom wireing that uses vey small relays to do the flashing as signaled off the regular turn signal leads by powereing the lites off the parking power.
They only work with the park and headlites in use.
If you notice, most all US made vehichles don't have true side flash but you will see them on many foreign 'labeled' cars.