My passenger side turn signal blinks really fast. Of course, I thought it was a bad bulb. Here's the catch- it works fine when my camper is plugged in to the 4 flat wiring.The end was corroded on the truck wiring so I cut the end off and was going to replace it, but I cant find a plug-in kit for it anywhere. Has anyone else dealt with this before? Thanks-Dan

 

You confussed me. Does it work OK, when the trailer is pluged in, and blink fast when nothing is pluged in?

 

Is this a factory 4-pole flat or an aftermarket? Also, does this "harness" have the factory 7-pin round within?

 

Correct.

As far as I know it is all factory. It does have the 7 pin on a bracket next to the 4 flat plug mounted right on the side of the hitch.

 

Anyone????

 

From my experience the flasher is faster when a bulb is out. The lesser resistance makes it flash faster. My F350 did this when I changed the rear lights to LEDS. If that is the case, when your trailer is pluged in it has the resistance to flash normaly.

However if your positive, there are no lights out? It doesnt make sense.

I wish I knew more about automotive wiring, and could give you more help. If you find the problem let us know.

 

On my older Ford Pick-Up, when I plugged in a trailer the turn signals blinked faster. What I was told to do was buy a heavy duty flasher and it would go away, I did and it did. The way the flasher worked on the old truck was; when the light was on the current heated up a wire, that would curl the wire and break contact, once no current was flowing the wire would cool down and then re-connect (just like the mini Christmas tree lights). Two lights, more current, the wire heated up faster. I don't know if this is the same on the new trucks or not, just an idea.

 

Sounds like you do have a bad bulb somewhere. Fix it first w/o the trailer, then see how it works w/ the trailer. As for the harness, you can get a replacement trailer tow harness from Ford. It connects under the L/R corner. Good luck.

 

Check your bulbs with an multi-tester. I have seen bulbs that appeared good, that were in fact bad.

 

Thanks guys, it was just a bad bulb. The bulb looked good but I changed it anyway, now its all working great.