Accidently backed a trailer into a hydrant. Smashed a tail light on the trailer. I replaced the light but now the truck has no power to the factory plug for the trailer. I have checked all the fuses that have to do with trailer hook up in the owners manual and they all look good. My question is do any relays come into play with this. I tried my service lit disc in my newer pc and it wont read it. Anyone have any ideas on this. Relays?????

 

All the rear lights work. NO one!!!!!!

 

The +12V power is not usually a factory wire. Its usually a wire run by whoever did the install straight off the battery, and it usually has a fuse holder inline.

 

Sorry I guess I wasn't real clear on this. I still have tail lights going to the trailer plug pins on the truck plug housing. This truck was purchased new with a trailer towing package from the factory. It is a 7 or 8 pin ( I haven't counted them ) outlet to plug the trailer into. Its a plug and play I have never run any 12 volt hot off the battery under the hood.

 

There are running lights red and yellow.
There are stop light function both sides.
There is left and right turn signal functions.
There is 4 way function,
Do any work? Or which ones do not work?
Is the trucks lighting ok?
It makes a difference on where to begin to look for the problem.
Good luck.

 

there are several different fuses involved. The TRUCK has fuses for the tail lights and brake lights.. The TRAILER has different fuses. I thought you said you had power to the rear plug, but the lights (trailer) dont come on. If thats the case, the wires on the trailer are bad... maybe ground wire broken... IF you have (lights) power at the plug.

 

there is a fuse under the hood dedicated to the trailer. it's on the driver side inner fender. Did you check that one?

 

The trailer outlet at the truck still has tail lights working and they work on the trailer. Nothing else at the plug or the trailer. I have checked all lights working on the rear of the truck but I have not checked the front. I do have a third light on a canopy but I believe this is tied into the brake light I have not checked it for function. I have checked all fuses per the owners manual that look like they may have something to do with the trailer or brake lights. All fuses appear to be good visually including underhood and in cab.. That's why Im wondering if this is possibly a relay problem. I will have my wife work all functions again tonight as I watch and see what works for sure including the third light for brakes on the canopy. Ill report back.

 

Here is what to do with a $5 to $10 volt/ohm meter.
Looking at the trailer connector you will see 7 pins.
Beginning at 11 o'clock is pin 1.
Counting 'counter clockwise' is pin 2, 3,4,5, and 6 at the 1 o'clock position.
7 is offset in the center area.
Pin 1 = left turn.
Pin 2 = ground.
Pin 3 = electric brake signal.
Pin 4 = right turn signal.
Pin 5 = 12v battery feed for the emg. battery charging and breakaway brake application should the trailer get away from the truck.
Pin 6 = running lights.
Pin 7 = reverse lights.
.
First test that 'ground' is ground and good with an ohm meter test to the frame from pin 2, then use that ground pin 2 as your reference to all other pins by testing all the functions because the rest of the circuits on the trailer uses the same reference pin..
To test brake lights on trailer use the 4 ways to test for pulsing 12v etc.
This will tell you either the trailer wiring and bulbs are good or not when plugged in.
Left and right turn the same way.
It's not a big deal the find which function is out and which side of the socket the issue is at.


.
Record what you have and don't have.
What you don't have is a problem on the truck and the circuit involved.
If everything is there the trailer has the problem referencing the pin vs circuit as above.
When you replaced the light did you wire back correctly?
Good luck.

 

Thanks BlueGrass Ill check these out. I haven't had time lately. Ill let the forum know how things go.

 

Ok Im back finally to report on this. I finally had to throw in the towel suck up my pride and take the truck to the Local Ford Dealer. They found the problem and it was an open fuse. When the service writer called me and told me that I said yeah sure I checked all the fuses and metered them I know there were no open fuses. He next said yeah that's what the tech found. Then he went on to say but it was in fuse box he did not know was even there on these trucks. I then said I went exactly by the owners manual as my service disc no longer played in newer pcs. Went to pic up the truck and they showed me this mistery fuse box it is back and under the and right next to the under hood fuse panels. It is not listed in the owners manual and I cant say weather or not it would be on the service disc as mine again wont open. So just a warning and FYI to anyone with one of these trucks 98 F150 with the factory trailering package. There is a fuse box not listed in the owners manual. Hope my $50 lesson helps someone in the future and thanks to all who tried to help me get this figured out.

 

I should have been more clear. That's the fuse box (holds 2 or 3) I was referring to.

 

You are correct it only holds 2 fuses. I thought you were talking about the 2 under hood power boxes. No harm no foul Tex my truck is lifted I should have got my step ladder out and looked from up above I may have seen the little jewel then.