Vehicle Trailer Lights - Work...but not on New Boat?

[Tin Man]

Went to pick up my new boat today and trailer lights would not work with my OEM 2003 Ford F350 Super Duty Trailer Connector.
Had to leave boat and will go back tomorrow with my second vehicle....a 2003 Toyota Sequoia SR5

While at BPS, used my round 7 pin plug tester (Round 7 pin to 4 way adapter with red test lights) in my truck’s plug and it tested fine.
Tested boat trailer lights on an employees truck, a newer Super Duty (2015+) and lights worked fine. We didn't even hook up to ball, only connected lights.

Came home and connected my truck to my old boat and lights worked fine. My old boat trailer is a 4 way flat and I used the same 7 pin round to 4 way flat adapter. They are LED lights.

The new boat uses a 7 pin round and has LED trailer lights.

We then used a testing device (Round 7 pin male and female, and 5 way flat connectors) that was made by one of the BPS techs (uses a small battery to power and is used to test trailer lights when no vehicle ism present) and when connected (battery portion removed) to my 7 pin round tester in the 4 way slot, lights worked fine.

For some reason, the new trailer when plugged into my truck does not work, but my other boat does.

I am completely at a loss for what this can be. I can only think my truck’s trailer connector is bad…, but it tests fine.

What am I missing?

Thanks!

 

[FuzzyGrub]

All my trailers use the flat four pin. Vehicles all had the same. When I picked up the pontoon boat, was surprised by the 7 pin round connector on the trailer. Luckily, the never used female on my 2016 4Runner worked. So, I’m new to them.

The only thought that comes to mind, something with the new trailer plug with your trucks receptacle. It’s not seating all the way or ground pin not making contact. Ie a physical issue, not a wiring one. When inserted in other receptacles, it is seating all the way.

PS: Glad I didn’t run into that issue. The dealer was 2 hours away. I hope you were close to the dealer.

 

[MrGiggles]

I would suspect a bad ground on the vehicle side. Perhaps the only connection you're getting is through the ball, may work fine on the old one but not the new one with fresh paint in the hitch.

I'd say the thing to do would be to load test each function with something like a headlight bulb that draws a few amps, and hook to the ground pin in the receptacle, not the chassis. If it is not lighting up the bulb, then move the ground clip to the chassis, if it lights up you have found your problem.

If you had a power probe, I would suggest just applying power to the ground pin and short circuiting it, if it pops the breaker in the probe then you know it's capable of carrying 10 amps, more than enough for trailer lights.

I have stopped using the flat plugs and converted everything to the round 7 pin RV connector, they're more secure and durable, with no exposed pins to corrode.

 

[FuzzyGrub]

I would suspect a bad ground on the vehicle side. Perhaps the only connection you're getting is through the ball, may work fine on the old one but not the new one with fresh paint in the hitch.

I like that theory!

 

[overboard]

You may need a different 7 pin adapter, my buddy and I ran into the same problem when we went to pick up a boat. I don't remember what the difference was, but luckily the guy at the NAPA we went to knew what we needed and the reason that we needed it.

 

[Still Afloat]

If your trailer doesn’t have electric brakes or other accessories that require power, just convert it to a flat connector. I use the round connectors on my bigger trailer and they are a bit of a pain to unplug.

 

[airshot]

In years past I have had issues with the round adapters, converted everything to flat four pin and never another issue. Something in those round adapters isnt alway right.

 

[jethro]

I'm so the opposite of what the last few have said... I'll never run a flat 4 trailer plug again. The 7 way is so superior it's not even funny. I guess it's worth noting that both my trailers have dual axles and electronic brakes, so maybe I'm a different use case.

 

[MrGiggles]

I'm so the opposite of what the last few have said... I'll never run a flat 4 trailer plug again. The 7 way is so superior it's not even funny. I guess it's worth noting that both my trailers have dual axles and electronic brakes, so maybe I'm a different use case.

Same. I feel like the round 7 pin plugs are more durable, seems like the flat plugs only last a couple years before the pins break or become too corroded to make a good connection.

Plus it's easy to swap or replace a round connector if you ever need to, the wires are held in place with screws. Flat plugs are molded so you have to cut and splice to replace them. There's also room for expansion if you ever wanted to add reverse lights, a 12v charge wire, etc.

 

[airshot]

I'm so the opposite of what the last few have said... I'll never run a flat 4 trailer plug again. The 7 way is so superior it's not even funny. I guess it's worth noting that both my trailers have dual axles and electronic brakes, so maybe I'm a different use case.

I would agree there...where I have had issues with the round 7 pin is when adapting to the 4 flat... When I had big trailers with brakes they were never an issue. But over the years I downsized to smaller trailers without brakes and usingbthe round to flat adapters created problems. Also there were changes to vehicle wiring from 2000 up to modern wiring....my Jeep is factory wired for both 7 round and 4 flat ( trailer tow pkg). My boat trailer has a flat 4 pin and it works fine in the flat 4 factory plug....but....if I plug in a 7 round and plug the trailer (4 pin) into the space on that round adapter, the trailer lights dont work, but they did on my 2000 Blazer. !!! I never tried to figure it out!!

 

[AlanT]

I would guess it's a ground problem since it's always a ground problem - possibly in the 7-pin connector. Your troubleshooting indicates it's a ground problem because troubleshooting a ground problem can make the pope say "aw s**t". Good luck.

 

[wis bang]

Since it has LED lighting, check the polarity. wiring error crossing + and - will not light LED's...

otherwise it is a ground issue

 

[Tin Man]

Update.....

After removing and inspecting my truck's pin connector, ground and positives were all good. No weak connections.

Since the flickering was on both my trucks and on the way home with the Sequoia, I started thinking the new 7 pin boat plug. I inspected it and thought I should press the brass tabs inwards slightly for improved contact. I did, and whooola! Pushed the plug in and lights turned on....and stayed on even when wiggling connector, no flickering.

 

[airshot]

Glad it was an easy fix....

 

[Tin Man]

Update #2….

Out camping right now on the Colorado River in Parker, AZ. My buddy brought his new Pontoon. We both caught a bass each! My boat stayed home.

My truck electrical plug is having problems. Went to connect my trailer’s plug and would not stay locked in unless I pushed the lid/cover down to hold it in place. If I lifted the cover, the plug slide off with very little effort.

At this point I will be looking for a complete assembly, from factory plug under and behind bumper to the 7 pin plug.

It’s always something when you are dealing with older machinery!

On top of that, my truck’s fuel gauge did not want to reach the full level even though the tank was at capacity. It slowly creeped to full as I drove down the road.

Love my truck, but she’s getting older!

She’s a 2003 Ford F-350 with the V10 , 2WD, crew cab, and 86000 miles.

 

[FuzzyGrub]

She’s old, but bet she can pull!