Another trailer tail light issue..imagine that.
However this is more of a question for @iMacattack of why? Or anyone else for that matter.
My lights have never been dunked. They sit up fairly high on the side guide boards, and I dry launch exclusively. When I installed them about a year ago, I soldered the harness to the lights, about 3” from the lights, so again, never been dunked. Each connection got heat shrink, and then the entire wire harness got an additional section of heat shrink over top. So its heat shrank from the light down the harness about 24”.
The soldered connection corroded and broke inside the heat shrink.
I used regular rosin core solder for automotive use, with regular paste flux. This obviously isn’t my rodeo soldering but this corrosion issue at the joint is.
Any ideas?
Mike all I can say is, the devil himself is involved in all trailer wiring!
No doubt.
Don’t solder. Crimp and heat shrink. Soldering can become brittle and brake when subjected to heavy vibration. 
Also consider that while you may not dunk the trailer it still gets wet. Rain while on the road and washing your boat.
It’s zip tied so vibration isn’t an issue, but yes, I’ve switched the joints over to marine connectors. Just curious on the corrosion as the solder joint was sealed with heat shrink. I’ve built countless motorcycles and vehicles and have never experienced this issue. It happened on both sides of the trailer. Just weird. The corrosion also didn’t track into the insulation.
9/10 times it’s always a grounding issue with trailer lights. I like to test the lights themselves with a 12v power source and work my way up.
Yep. But my concern is why did the solder joint corrode? Even though it sealed under 2 layers of heat shrink, and never submerged.
Was it marine heat shrink or regular heat shrink?
Regular.
Gotta use marine grade. It has a sealant built into it.
This
I have a hard time soldering without creating an edge that pierces the heat shrink. I gave up soldering
@MikeCockman soldering can create a strong reliable connection, however it’s typically not recommended for trailer wiring or most marine applications. Mainly due to its vulnerability to vibration even when Zip Tied. Plus it’s still susceptible to heat and potential corrosion, as you’ve experienced. Crimping is the generally recommended method.
Cheers
It’s funny, because In the Motorcycle world, you’ll get run out of a shop using a connector, and there are areas that you don’t have enough room to use connectors. Even in school Harley Davidson teaches or atleast taught, correct soldering techniques. And we all know nothing vibrates like an old Harley..
.
Chalk it up to a lesson learned I guess.
I hear Harleys are a b!tch to pole in the shallows. LOL
They don’t turn worth a damn either.
Mike, I have been thinking about this a day or so, and cant think why you have this particular issue. Yes, Adhesive Lined Marine Head Shrink is a must, but you are identifying the failure mode as a cracked solder joint.
I solder all my connections when wiring a trailer. My current lights and wiring are over 10 years old, zero issues, as bright as can be. I use an electronic solder also (not the plumbing solder). This is on my Bay Boat that the lights get dunked every time. I have wires that are zip tied to the trailer also.
This is conjecture, but could it be crevice corrosion within the solder joint weakening the connection, then breaking due to vibration? The non marine grade heat shrink allowing the salt water in? If so, thats an interesting failure mode!
I might get flamed on this, but I Do NOT like crimp connectors on trailer wiring, even the Ancor Marine Grade crimps that have the adhesive lining. Reason: when you crimp the heat shink on, the outside can be pierced and that will eventually create a problem. Also, there is a significant difference between the diameter of the crimp versus the wire, making effective use of heat shrink difficult. With solder, there is little difference in the diameters, its easy to heat shrink effectively.
Just thoughts to help figure out your direction. I think I would resolder but this time using Adhesive Lined Marine Grade Heat Shrink.
I don’t know either it’s definitely had me scratching my head.
I know marine grade heat shrink is the better option, and had I believed water intrusion would’ve been a concern I’d certainly used it.
However with the connection being “high n dry” I didn’t think it was necessary. Especially with it being doubled up, (the individual wire heat shrunk then all of the wires heat shrunk again). The solder joint was solid, but the wires on either side of joint just corroded away. The corrosion didn’t track up the insulation though, just either side of the joint.
The lights have tinned wire, the harness is not. Just standard trailer wire harness.
I also had a sealed marine ring connector fail from corrosion at the front of the trailer. So they are not idiot proof either.
At any rate, lesson learned I guess.
I think any debate should start with an objective starting point. In this case what are the ABYC standard?
ABYC Standards,
11.16.3. WIRING TERMINALS
11.16.3.1. Wiring connections shall be designed and installed to make mechanical and electrical joints without damage to the conductors.
11.16.3.2. Metals used for the terminal studs, nuts, and washers shall be corrosion resistant and galvanically compatible with the conductor and terminal lug. Aluminum and unplated steel shall not be used for studs, nuts, and washers.
11.16.3.3. Each conductor-splice joining conductor to conductor, conductor to connectors, and conductor to terminals must be able to withstand a tensile force equal to at least the value shown in Table XVI for the smallest conductor size used in the splice for a one minute duration, and not break.
11.16.3.4. Terminal connectors shall be the ring or captive spade types. (See FIGURE 17.)
EXCEPTION: Friction type connectors may be used on components if
1. the circuit is rated not more than 20 amperes or the manufacturer’s rating for a terminal designed to meet the requirements of UL 310, “Electrical Quick-Connect Terminals”, or UL 1059, “Terminal Block”s, and
2. the voltage drop from terminal to terminal does not exceed 50 millivolts for a 20 amp current flow,
and
3. the connection does not separate if subjected for one minute to a six pound (27 Newton) tensile force along the axial direction of the connector, on the first withdrawal.
11.16.3.5. Connections may be made using a set-screw pressure type conductor connector, providing a means is used to prevent the set-screw from bearing directly on the conductor strands.
11.16.3.6. Twist on connectors, i.e., wire nuts, shall not be used.
11.16.3.7. Solder shall not be the sole means of mechanical connection in any circuit. If soldered, the connection shall be so located or supported as to minimize flexing of the conductor where the solder changes the flexible conductor into a solid conductor.
EXCEPTION: Battery lugs with a solder contact length of not less than 1.5 times the diameter of theconductor.
NOTE: When a stranded conductor is soldered, the soldered portion of the conductor becomes a solid strand conductor, and flexing can cause the conductor to break at the end of the solder joint unless adequate additional support is provided.
11.16.3.8. Solderless crimp on connectors shall be attached with the type of crimping tools designed for the connector used, and that will produce a connection meeting the requirements of E-11.16.3.3.
11.16.3.9. The shanks of terminals shall be protected against accidental shorting by the use of insulation barriers or sleeves, except for those used in grounding systems.