Folks, There may be an answer here somewhere and I hope I didn't miss it by not reading the forum thoroughly. Here is my question.... My 01 F150 keeps blowing fuse #19 as soon as I hook up a trailer and use the right turn signal..... I need to stress this only happens when I hook up to a trailer with a 4 wire flat connection ( I haven't tried the 7 spade connection) and apply power (turn on the lights) and it only affects the right side... the left works just fine...The truck came with a sport package..... do I need to change out/add a relay??? I would like to solve this issue so I can tow safely....... Any help is greatly appreciated......

 

I could be wrong here,but the 7 wire connector I THINK is actually for a Power Brake booster for a large trailer.
Concerning the Fuse blowing,Since everything works except the right side under certain conditions,My guess is the problem is not in the truck,rather trailer harness.
If you have access to another vehicle,I would plug the trailer into it,and see if the issue follows it.

 

Could be?

You have a short circuit in the right brake/turn signal circuit (green wire) on the trailer. Might be a corroded/shorted bulb in the tail lamp housing) or a chafed wire along the trailer chassis. If the wiring goes through the frame rail, check those points first as trailer manufacturers often neglect to install insulating bushings.

 

if you have a 7 spade connector at the rear of the truck, it is tied to the 4 pin connector on 4 wires... the other 3 wires are +12 volt (battery charge), brake signal, and backup light or ground wire, depending on how it was wired up.

 

The problem follows the truck. It doesn't matter what trailer I hook up too. I've used my buddies trailer for his jet skis, a tow dolly from U-haul (In El Cajon) and recently a U-Haul Auto Transport (here in Klamath Falls (I was trouble shooting the Auto transport- I needed a power source)). This is a Ford Factory towing harness. I really don't have the 97 clams for another harness at this time and I sure hope the problem does not lay in the multifunction switch. The next step I guess is a pin to pin with a multimeter (barrels of fun)

 

I would look closely at the connector pins for damage of some sort both in front and in the rear.
If the fuse blows only when any trailer connector is plugged in, the socket/connector may have some issue.
The right turn/stop is the end pin. The next one is the left turn.
This is the only place anything happens.
Make sure the fuse you place is a 10amp rateing.
Just when does the fuse blow?
Cold when no lights are on?
Only when the turn signal is operated?
Only when the brake lamp is lighted?
If the flat connector was wired seperately, there may be an error.
On the 7 & 4 pin connectors, the following pin connections are;
1. white= gnd.---------------- 4 pin-----> wht = gnd.
2. blue= electric brake.---------------------- -------------------
3. green= tail/lic.------------------------> brn = tail/lisc.
4. black= battery charge.------------------ ---------------------
5. red=left stop/turn.--------------------> yel = left turn/stop.
6. brown=right stop/turn.----------------> gn = right turn/stop.
7. yellow= center aux. ------------------------------------------

.
Make sure the 'LEADS" match, not the color codes because they are not the same between the two connector types.
Good luck.

 

Pin to pin check revealed no adverse problems, 12.5V DC through and through. Resistance check revealed less than .05 OHMs. Both the 7 spade and 4 flat connection showed good continuity and proper function. The fuse did not blow with test equipment hooked up (I have a continuity tester for the four wire flat.) I may just need to clean my connections and coat with dielectric grease. This problem only seems to occour when I hook up to a trailer and the circuit is hot ( I need another set of eyeballs to verify this). It could be the relay- is there any way to test it?

 

Verify the voltage at the end connector pin pulses with the turn signal on, with no trailer connected.
If it does the circuit is ok and there is a shunt to ground on any other trailer you connect.
Maybe the trailers are wired in error for some other towing vehichle that is also wired incorrectly with a ground on that pin in the wrong place.
This is why there are color code and pin number standards so any trailer can be plugged in without issues.
If you can't find the issue now, I'm out of ways to help.
Good luck.

 

Appreciate the help....yes the voltage does pulsate- anywhere fron 12.5-5.1V DC- w/ no trailer connected. I'm going to keep plugging away at it it 'till 'tis solved. Hoping my companeros have a slow day so I have an extra set of eyes to help me...........

 

I solved the problem, it was so simple you all are going to laugh. The problem was the engine was on while connecting the trailer electrical. So engine off while hooking up and the problem never returns

 

Honestly, I would still wonder why!
Hooking up with the engine running should not have an effect on a fuse.
Reason why I am doubtfull is what would happen while towing if the connector became intermittant? Blow a fuse? It's not supposed to work like that.
If the lamp loads is that near the fuse blowing limit, some investigation should be done as to why.
Normally one stop/flash lamp on a trailer does not take 10 amps.
As a point of technical interest 14 volts times 10 amps is 140 watts. The turn/stop lamp is about 15 to 25 watts +/-.
I have plugged up both 4 and 7 pin connectors at night and never saw this kind of issue.
To have it as a norm is not good.
If it works for you and you are satisified, then good luck with it.

 

Yep,Gotta agree.Personally I think it will come back to "bite you" at some point.

 

This does not solve your problem. I got yet another trailer today (I've had this issue on three different trailers so you can all quit the conspiracy theories about poor wiring..it's the damn truck's system.
I turn all power off...won't even let the tail lights on when I do it, and it's the only thing that seems to keep the thing from blowing, yet today on yet another trailer, I had only the radio going, and the damn thing blew a fuse again..absolutely ridiculous, so aside from the BS of pulling an entire truck apart, please somebody tell me what their final solution was.

 

Hello Bill,
Fuse 19 is for the right stop/turn signal lamp only.
It has nothing to do with the radio.
Fuse 20 is the left side.
Have you ever saw fuse 20 blow for the left side?
Only difference between an engine running and stopped for electric is at stop the voltage will be about 12.0 +/- while motor running will be about 14.5+/-.
Granted the power consumed and current would be a bit higher with the motor running and the dash switch on, but never so much higher that it would blow a 10 amp fuse with just one lamp on the trailer.
These fuses are seperate for each side as no other circuits are on the fuses by design for safety.
A single lamp or a combination lamp would still never draw 10 amps unless the filiment was shorted or faulty or the lamp socket was causing a problem.
You can have two different stop/turn lamp options.
One a single filiment lamp or a dual filiment lamp that works as a tail and stop/turn.
The dual filiment lamp fools a lot of people in that it has a center tap that is the ground for both filiments and causes funny problems when the ground is not good.
.
Not that I have your answer but look at it this way to be sure the trailers don't all have a problem that is the same cause.
It has to be a short that causes 10 amps or more to flow.
This is the 'only' way that fuse will blow.
It's the same as with any other circuit and any other equipment.
It still sounds like that circuit is getting grounded at plugup time in some way.
It just may be marginal such that at 12 volts without the motor running there is just enough less current not to bring the current quite to the point of blowing the fuse.
One other thing is if a fuse is subject to being over loaded to many times to near it's limit it will blow from it's element fatigue at a lesser load at an unpredicitable time.
Circut breakers if tripped to many times finally won't hold a reset and need to be replaced.
Good luck on it.

 

Bluegrass,
What I was saying that I had turned EVERYTHING off, as I have to do with each trailer...can't even anything at all on, and then everything is good. I had the radio on, with the door open while I was plugging the trailer in and ...no lights.
Be clear, I blew the fuse on another trailer, which caused me to realize that it was occuring on my boat, on my sea doos, and on this enclosed trailer. I realized it was only the right side, then realized there was a specifc fuse for it.
Ran that trailer to Sturgis and back with no problems, plugged and unplugged several times with EVERYTHING OFF...and no problems, everything worked.
I picked up a travel trailer on Thursday last week (when I posted) and lo and behold, I left the radio on...no more lights on the right...running/turn/brake...nuttin'.
So, the only way I'm having any luck is by being sure absolutely everything is shut off. I'm certain it's not 4 different trailers having the same issue. It's simply that the damn truck is wired poorly and there is enough draw "somehow" to cause this fuse to blow. I will be trying a circuit breaker this week...maybe that will be my fix for now, but beyond that, it's a pretty sad thing to be able to find this same problem occurring all over the internet without Ford figuring the fix.
I did check wiring at the harness and plug...everything was working fine on the harness and at the plug when the fuse was new.