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When you're about to hit the road, the last thing you want is to discover an issue with your trailer's wiring. The Curt LED 4-Way Flat Connector Tester makes it a cinch to verify your vehicle's wiring is in perfect working order before you hook up your trailer. With its simple plug-in design, three bright LEDs promptly indicate functioning circuits for the right turn, left turn, brake, and running lights. No more guesswork—just a quick confirmation that your setup is ready to roll.
If you're dealing with a pesky wiring problem, this tester is your go-to tool for quickly identifying issues. It's designed to clearly show whether the issue lies within the vehicle's wiring or elsewhere. The lights provide instant feedback, letting you know if it's the right turn, left turn, or tail lights signal that needs attention. It saves you from unnecessary troubleshooting and diving under your vehicle without direction.
Small enough to fit comfortably in your glove box, this tester is a ""just-in-case"" tool that becomes invaluable when issues arise. Whether you're renting a trailer last minute or regularly pulling yours, having this tester on hand means you can verify functionality without needing a trailer present. Its compact size ensures it's always within reach when you need it most, making last-minute checks a breeze.
Thanks to its straightforward design, you won't need an engineering degree to use this tool. Simply plug it in and the LEDs will show you what's happening with your wiring. This ease of use also means others, like a neighbor or family member, can borrow it and use it without needing your guidance—perfect for community wiring checks or last-minute borrowing.
Unlike complex voltmeters or complicated setups, the Curt tester provides immediate visual confirmation of your wiring's status. Its built-in design means you can perform tests solo—just hook it up and toggle your vehicle's signals. You'll instantly know if the setup is up to code or if adjustments are needed, all without second-guessing which circuit is which.
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Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
Hey everybody, Ryan here at etrailer. Today, we're going to be taking a look at the Curt four-pole vehicle side trailer, wiring tester. So, if you guys have ever towed a trailer before I'm sure you have encountered this problem. You get all hooked up, and kind of do a walk around, you know you kind of do a pre-trip before you hit the road. You check a few things out, one of them being the lights. And, of course, you turn your blinkers on.
Maybe you have a light out at the trailer. You hit the brakes or the tail lights and something's wrong. And then this kind of turns into a headache. You know, you're, you're checking your vehicle side, checking fuses, making sure everything's good there. Then, you get the going on the trailer side.
It's kind of just a big mess. And one thing you can do to isolate that problem is use a vehicle side tester like this. So, the way this is going to work, is it's going to plug into your vehicles four way flat connector. All right, and then that's going to isolate the problem. So, once you plug this in, you can run through all of your signals and your lighting functions.
And if they all work back here, then you know, okay something's going on with my trailer and you can focus your time on that. If you don't have all your functions back here chances are good. You could say, okay, trailer's probably okay. I probably have an issue with my vehicle side and you can focus your energy there. So, at the end of the day, if you do have an issue, it's a great little tool that can potentially save you a ton of energy.
So, whenever you are plugged in to your vehicle side, you can test the function. So we're going to have our left turn signal, our right turn signal, our taillights, and our brakes. So, since these lights are LEDs, really easy to see, even on a sunny day like today, which is convenient, especially if you're by yourself, kind of trying to, you know if you have miring stored inside you can hold it up or mount it up and check it while you're in the driver's seat, so you ain't got to get out of the car every time. But, since we don't have any labels or anything here, I figured it'd be useful to share what lighting function illuminates the light on the test, or if that makes sense. So, this light here should turn on when you use your right turn signal, the one next to it should turn on when you use your left turn signal, both of these lights should illuminate when you apply the brakes, and this one should come on whenever you have on your tail lights. So, let's say if you're, you know, testing your, your right turn signal, this one should be flashing. See, this one isn't, but this one is, okay So, you're still getting something to happen, but on the wrong circuit. So, that could help kind of direct you as well to get it figured out. You may have a short or something like that in the electrical system, and that could be looked at. So, when it comes to this tester, honestly, this is probably the last one you'll ever need, unless you lose it or something like that. Things are actually pretty, pretty stout. They're pretty solid. These are actually the exact ones we use here at the shop. And we use them day in and day out, all the time, and we've had them for years. They still work like they should every day and they really take a beating, and they just continue to work. So, for the average person to use them, occasionally, I mean this should last for the life of your vehicle or the life of your trailer, and then some. So, really nice, you know, it does have a key ring holder on the top there. And what we do, here at the shop, is usually put a zip tie or some type of key chain on there just to make a little larger so we can hang it up. If I had, you know, if I was going to keep one in my personal vehicle, something like that, you know, I'd probably end up using a key chain with my trailer lock and everything else on it, throw it in the glove box, so you always have it. So, it's a little nice touch and something I thought was worth mentioning. So, as I mentioned, this could work for your four way flat type connectors and it just plugs right in, just how you'd plug into the trailer side. And if you have multiple vehicles or different trailers, things like that and you need a different type of tester, not a big deal. We offer other ones as well. Whether you have a five way or a round seven-pole something like that. There's going to be a tester similar to this available here. That way you can use it for that wiring as well. And that'll finish up our look at of the Curt four way flat trailer, wiring tester..
Excellent Product and service!!!
everything worked perfect
Handy and works well.
Excellent service(2 days) I have not used the product yet
Ordered product Tuesday it delivered Saturday. Good tester.
This is a great inexpensive and easy to use tester.
It's just a tester, and it works. Fast shipping, packaged well.
Used during installation of the C5602 harness.
Works a treat!
EXCELLENT...... START TO FINISH. Fantastic service, great prices, quality products. Very handy little tool. Thanks again, Bill B. in Michigan
Best little item to have laying around. I have a 6 pole harness and adapter and wasn't even sure if the 4 pole connector worked. Plugged this in and 30 seconds later, I had the results.
Helpful. However, it does not put a load on the signals, so if you have a weak 12-volt or ground connection to your trailer-light signal converter, it will still indicate that the system is working properly.
Simple to useThis tester is well worth the few dollars that it costs. Allows you to easily test your wiring harness during installation without having a trailer available. Also allows you to verify that the vehicle wiring is in working order when troubleshooting trailer lighting issues.
Handy little tool to have on hand to verify your wiring. Quick and painless testing for wiring up a 4 pin connector. Did require a 2nd pair of hands to hold it up while I tested all the lights and functions.
Once I deciphered how to interpret the lights, I was extremely pleased with the Tester. Your installation video for my wiring harness was where I learned how to interpret the lights, as there are no instructions included with the tester.
Perfect. I use this all the time to ensure trailer lights are working before hooking up. Saves time in diagnosing problems. Excellent product.
Worked as intended. Very easy and was needed to test the wiring harness.
Order has been received.
Installation was completed 3 days later.
The installation video was most helpful on your site.
The followup on the order has also been impressive.
The unit is now in service and operating as described.
This item cost significantly more than an "off the shelf" harness but the extras such as the overload protection module and custom connectors seemed to add value. In fact, I am very pleased thie the unit, process and ease of installation. I would do this again without hesitation and would recommend your site to anyone.
The time and frustration usually dealt with in performing this type of installation in the past make this a very worthwhile investment.
Issues I did experience:
The tracking of the item from shipment and through 3 handling centers in the U.S. took 4 days
The handling of the package once in Canada, through 3 centers took 9. This delay over the border meant that I missed my first opportunity to utilize the vehicle on its' first assignment. Unfortunate but not really a reflection on etrailer.
The mounting bracket ordered did not fit on the trailer hitch I received, which was a round main support with no flat surface for the mount bracket. Once I was able to create a mount location, the next challenge was the extreme pressure needed to seat the electrical socket into the bracket. Eventually this was accomplished. Upon first use, the socket easily slipped back out of the bracket. Reversing the bracket, the result was the same, difficult to insert, easy to push back out. I have made other arrangements without the mounting bracket.
Overall, I am pleased with the result and would do it all again.
Thank you and etrailer for the follow up and the product.
Great to have in your tool box.
Tester made it easy to verify a correct installation!
Worth its weight in gold! Now I'll always know if a trailer light problem is on the trailer, or on the car.
1 year old and still works great! Sure makes testing trailer lights easier. If there is a problem, you know if it's the tow vehicle or the trailer in an instant.
Nice to have before putting back all the panels on the RAV4.
Tester worked fine, showed I didn’t have running light, got replacement harness from trailer, still no running lights. Phone call to tech service not helpful, call to BMW won’t discuss it, so I have a trailer W/O running lights.
On your video they had
Very handy for testing harness and protecting the pins.
Info for this part was:
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James
5/16/2025
This little tool works great. Ive used it a few times to make sure everything was working and troubleshooting a blown tail light on my trailer. Handy little tool to have in the glove box if youre towing.