Wiring issues can be frustrating and time consuming to fix, especially when you are not sure where to begin troubleshooting. When your trailer lights aren't working, your trailer is not working, and you are losing valuable time and money. Using the following information and testing procedures, you should be able to locate and eliminate the most common issues encountered during or following a 4 or 5-Way wiring harness installation and get back on the road as soon as possible.
When it comes to troubleshooting a wiring installation, testing is everything. A lighting problem can originate at any point along the wiring on either the tow vehicle or the trailer, so it is important to determine not only what is causing the problem, but where it is located. The question the troubleshooter will find themselves asking is "There are so many things to check. Where do I start?"
Perhaps the most helpful thing you can do to start troubleshooting is to determine whether the problem is on the tow vehicle or on the trailer. When you use your trailer to test, you have no way to know for certain whether the problem stems from an issue with the wiring harness because the trailer's wiring system is still part of the equation. Testing the vehicle without the trailer will allow you to separate the wiring system into manageable sections.
Use the testing procedure described in Method 1 to check for function at the vehicle's 4-Way plug. If all the functions come out correctly at the vehicle plug, you will know that the problem only appears when the trailer's wiring system is connected and you can concentrate your efforts on the trailer.
The most helpful tool to use will be a 12V probe-style circuit tester. Click here to
see our circuit testers.
In addition, you will want to have basic wiring tools
on hand. These include electrical tape for repairing connections, a wire stripper for cleaning up wire
ends, dielectric grease, and various wiring fasteners like
butt connectors, quick splice
connectors, or ring terminals, depending on the type of repairs required.
Wiring kits that include
these items are available.
A trim fastener removal tool can reduce the time needed to access your tail light wiring, particularly in SUV and minivan applications, but a flat-head (slotted)
screwdriver will often work just as well. A power drill will be used to install the screws for the ground wires. A 12V battery can also be useful
for testing trailer lights in situations where you don't have access to the vehicle or you suspect an issue with a particular trailer light.
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