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Brophy Circuit Tester for 4-Pole Flat Trailer Connector

Brophy Circuit Tester for 4-Pole Flat Trailer Connector

Item # F4CT
Our Price: $15.30
Electrical Tools
Shipping Weight: 0.04 lbs
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Circuit tester plugs into your 4-way flat trailer wiring harness and identifies lighting problems. Labeled LED lights illuminate to show which functions are working properly. 1-800-940-8924 to order Brophy electrical tools part number F4CT or order online at Free expert support on all Brophy products. Great prices and Fastest Shipping for Brophy Circuit Tester for 4-Pole Flat Trailer Connector. Electrical Tools reviews from real customers.
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  • Reviews (186)
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Brophy Electrical Tools - F4CT

  • Testers
  • Circuit Tester
  • Tow Function Tester
  • Brophy
  • Black

Circuit tester plugs into your 4-way flat trailer wiring harness and identifies lighting problems. Labeled LED lights illuminate to show which functions are working properly.


  • Circuit tester plugs into your trailer's wiring harness to check the conductivity of all the circuits between your vehicle and your trailer
    • Quickly identifies lighting problems
  • Labeled LED lights indicate which functions are working properly
    • Tail: tail lights
    • LT: left turn signal and brakes
    • RT: right turn signal and brakes

F4CT Brophy 4-Way Flat Circuit Tester

Video of Brophy Circuit Tester for 4-Pole Flat Trailer Connector

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Brophy 4-Pole Flat Trailer Connector Circuit Tester Review

Hey there hollers. Today, we're going to be taking a look at Brophy's LED Circuit Tester. It's available in a 4-pole or 5-pole connection. Before you hit the road with your trailer, we always recommend testing things out to make sure it's working properly. One of the most important things to test out is the lighting so that others know your intentions around you while you're going down the road. Here at etrailer, we recommend testing your light at the source, which is your vehicle.

That's where this Brophy 4-Pole Flat Connector comes in, because when you plug in your trailer and you have a fault on your trailer, you're not going to necessarily know where the fault lies.With our Brophy 4-Pole tester we can eliminate the variable of our trailer and determine whether or not our vehicle side is working. We simply plug it into our 4-pole connection and then we can run through our functions. You'll want to make sure you have your left turn signal, your right turn signal, your tail lights and your brake lights. Now that you know that your vehicle's working properly, if there we're any problems with the lighting on your trailers end, you can isolate it just to your trailer, make those repairs, and then you're ready to hit the road. And that's going to complete our look at Brophy's LED Circuit Tester..

Customer Satisfaction Score:

Customer Reviews

Brophy Circuit Tester for 4-Pole Flat Trailer Connector - F4CT

Average Customer Rating:  4.9 out of 5 stars   (186 Customer Reviews)

Circuit tester plugs into your 4-way flat trailer wiring harness and identifies lighting problems. Labeled LED lights illuminate to show which functions are working properly.


This works just as promised and makes checking the wiring connectors much easier.



This product has performed well over the past year.


Works great, a lot quicker than a multimeter. And not very expensive.


Ordered hitch receiver with wiring for bike rack installation on 2019 Ford Explorer. Everything arrived in less than a week. Crawled under the car with my burly son and finished the installation in about an hour. Toughest part was getting the exhaust hangers off. Didn't have a tool for that. Online installation video was a big help. Hitch frame rubs against right side exhaust hanger, hence the four star rating instead of five. Exhaust still appears to be level and no weird noises, so not an issue. Get the little plug in light tester. It's worth it, then keep it in the glove box. Haven't purchased bike rack yet, but no concerns about the hitch.


Worked great


So easy to install and works perfectly


This tester is simple and easy to use and a great way to do a quick check of your trailer plug.


Great product at a good price and shipped extremely fast!


Grounding issues are always a problem with trailer lighting (in my experience), and it is great that there is a product specifically intended to provide grounding continuity from the light itself to the tow vehicles wiring. Too many systems rely on a short pigtail attached directly to the trailer and a connection at the trailer ball.

I am hopeful that this will be a long-term solution.


This was a relatively simple and straightforward installation on my 2019 Volvo XC40. The directions were clear, although the black and white pics can be a bit hard to follow. I would add the following points. First, the left plastic rail in the spare tire compartment needs to be removed, and it has an odd hook at the front that is a challenge. It will come with some wiggling. It's equally challenging to put back on. Second, I used the Volvo ground terminal to ground the T-One module. Third, I ran the wire from the module to the positive terminal down through a grommet in the spare tire compartment, then along the brake lines under the car to the battery. This was easy to do with the vehicle on a hoist, but will be more challenging if you don't have access to a hoist. I removed 2 of the protective panels under the car to route the wire. It was fairly straightforward. The product works as advertised and fits very well in the car.


This is a keeper everyone with a trailer wiring harness needs to purchase yes


Easy tester for trailer wiring harness. Made it easy to check as I installed new wiring harness and ran wires - to double check all worked before putting all the trim back in place.


I bought this at the same time I bought a Hopkins Plug-in Simple Wiring Harness With 4-pole Connector. It worked exactly as advertised and let me test the wiring harness installation in advance of hooking up a trailer. Both products are excellent, and the folks at etrailer exceeded my expectations in all areas, particularly the very fast response to my order.



Still working great and very helpful to make sure all is well with the wiring harness in the truck. Definitely still recommend.


Overall a great product. Served it's purpose. Only reason I purchased was because I didn't have a trailer immediately available to test the electrical wiring I installed on the vehicle. If you have a trailer, I wouldn't bother spending the money on this, but for those like me that didn't have a trailer at the time, definitely a must-buy. Easy to use, and can help troubleshoot any issues you may have with your wiring.


Rock solid performance


Products I ordered were delivered faster than expected with no issues. Keep up the great work. I would highly recommend this company. Install went great and according to on-line instructions on their website.


While the product itself was excellent, the instructions were on the ambiguous side. Forget the instructions, and just watch the video to Hook Up----Suby's are so easy!!


Works great and totally handy


Works good.


Worked great confirming the integrity of my trailer light install.


Once I had the harness installed. It was great to plug the tester in and check my work. I would highly recommend this tool.



Well, Ive had this little tool for a year. Now I dont use it very much, but I recently noticed my trailer lights werent working when I plugged them into my truck. The tester helped troubleshoot the problem quickly and I was back in business. So again I work recommend buying this tool and keep it in your towing vehicle. You never know when it will come in handy.


Etrailer equipment is easy to install and gives a finished custom look. They provide instructions, videos, and guidance throughout the process, so making a mistake is nearly impossible. The performance and quality of the equipment is unequaled and function is flawless. I rarely bother with reviews, but they are deserving of my time, and potential customers should know they can't go wrong shopping here!


Great product to be able to test your electrical install before you close it all up and try to hook up a trailer and cross you figures it was done correctly. I was able to install my own wiring harness and use this tester to make sure everything was good. Well worth the extra few dollars.


Everything was as expected, wiring was plug n play and didn't take long at all to hook up ,
Thanks etrailer


Product was easy to install as shown in the videos. For my XTerra the connection into the wiring harness was hard to find. Recommend getting the tester to assure you have a good working connection and can prove you are generating voltage for the indicators, taillights, and brake lights.


What is there to say about this. Easy to use, just plug it in, the LED lights are clearly marked. If your wiring is correct, the correct led lights will show.

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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Dustin K
Installed by:
Dustin K
Employee Chris R
Video Edited:
Chris R
Employee Amanda M
Written by:
Amanda M
Employee Jonathan Y
Video by:
Jonathan Y

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