A Wise Mechanic Said - Check The Simple Stuff First...

zelinadc · May 20, 2011

Good thing I can laugh at myself. I hooked up my utility trailer and noticed the RH signal was out. Its fairly new and has LED lights so I suspected the 4 pin plug on the truck may have some corrosion. 04 F150, and PA winter roads are salted to death. Sure enough one of the legs in the connector was dead. However, the truck signal was fine. I ASSUMED Ford simply spliced the harness somewere in the rear to catch the signal lights.....

Since my truck had the tow package, I had the 7 pin connector next to the 4 pin flat, same thing no RH signal on that connection. A few years back, I spliced in one of those LED light bars. I had long since taken that waste of money off, and ASSUMED corrosion where I made the connection. In fact there was. This time I was going to fix it right, cleaned up the corrosion, soldered and shinktubed the wires, wrapped 'em up with Super 33. Perfect! Went to test the trailer connections - nothing on the RH??? Ok its something a bit more complicated...

Climbed under and pulled harness connections apart... clean and dry. I started to look for this "splice" in a section of the rear harness, and since I had it disconnected, I removed it from the truck to the workbench. Got my meter out, and started ringing out the wires... no opens???? WTF...

Then it struck me... what if Ford put the trailer lights on their own circuit and its own fuse??? Pulled the owners manual, and sure enough... all the trailer wiring is seperate, and independently fused from the vehicle wiring. Fuse #38 10amp BLOWN! Popped in a new fuse, and all is well.

Do GM trucks do this, or is this a Ford thing? Makes sense to protect the vehicle harness, but if you are not aware of this little fact - can lead to wasted time chasing wild geese. Oh well, at least I cleaned up all the connections, put some dielectric grease in and put it all back neatly... and got a good laugh at myself.

TexasAl · May 20, 2011

It happens to the best of us. I am not sure if GM has the same setup, but I can relate to your story. I've spent lots of time chasing those "wild geese", only to find that it was a 2 minute fix.

zelinadc · May 20, 2011

It happens to the best of us. I am not sure if GM has the same setup, but I can relate to your story. I've spent lots of time chasing those "wild geese", only to find that it was a 2 minute fix.

At least we can bask in the satisfaction of solving the problem... albeit the Looong way!

NitZ · May 20, 2011

It happens to the best of us. I am not sure if GM has the same setup, but I can relate to your story. I've spent lots of time chasing those "wild geese", only to find that it was a 2 minute fix.

Sometimes we just can't figre out why it would be a fuse! Haha! An old technician told me when I started in mechanic: whatever the problem you have, always check battery and fuse first. After that you will be sure and have no doubt that the problem isn't related to that section.

ChevyTech77 · May 20, 2011

We call it the K.I.S.S. method.

Keep It Simple, Stupid.

zelinadc · May 20, 2011

We call it the K.I.S.S. method.

Keep It Simple, Stupid.

Amen to KISS... sometimes stupid creeps back... The clue to the seperate circuit was the truck light wire was orange/blue and the trailer side of the harness was solid green... thats when the "light" went off.

ChevyTech77 · May 20, 2011

We call it the K.I.S.S. method.

Keep It Simple, Stupid.

Amen to KISS... sometimes stupid creeps back... The clue to the seperate circuit was the truck light wire was orange/blue and the trailer side of the harness was solid green... thats when the "light" went off.

I've been doing it for close to 20 years as a career. KISS will ALWAYS creep back in from time to time.