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Circuit Tester Kit

Circuit Tester Kit

Item # 40376
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Electrical Tools 40376 - Circuit Tester - Draw-Tite
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  • All Info
  • Reviews (23)
  • Q & A (0)
  • Videos (2)
  • Photos
  • Why etrailer?

Draw-Tite Electrical Tools - 40376

  • Testers
  • Circuit Tester
  • Draw-Tite

Circuit Tester Kit


  • Heavy-duty tester signals with a light and a buzzer
  • Tests low voltage up to 28 volts
  • Finds electrical shorts
  • Checks circuits from a distance
  • Checks polarity
  • Checks battery drain
  • Kit includes:
    • Alligator clip
    • Hook

40376 Circuit Tester Kit

California residents: click here

Video of Circuit Tester Kit

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

Video Transcript for Circuit Testing a Vehicle 4-Pole

Today Im going to show you how to test the functionality of a trailer four-way connectors. What youre going to need to do this is a circuit tester and a buddy in the drivers seat to operate the taillight functions. The first thing were going to test is the taillights themselves. Hit the taillights. (beeping) that means thats working. The next thing were going to test is the left blinker.

(beeping) That works. Then were going to test the brake light function on that side as well. So, hit the brakes. (beeping) That works. Then for the right blinker (beeping).

Now the right brake (beeping). Now we know that this four-way connector is functioning.

Customer Reviews

Circuit Tester Kit - 40376

Average Customer Rating:  5.0 out of 5 stars   (23 Customer Reviews)

Circuit Tester Kit


Works as described, no issues. Would definitely purchase again.


Off cause Etrailer is the best ! Never regrets order things from them!


This is my second Lisle circuit tester. I purchased to replace a unit I lost. These are very well made and worth the extra spend. The Customer Service from e-trailer is second to none and I'm a repeat customer due to the help these folks will render.

Still works well and is still in great shape. Thanks for asking.
Scott P - 09/29/2016


Ordered several electrical connectors,wire and a wire tester .. all items came in good condition ,looking forward to using the tester as soon as I can I am sure it will do the job.


Excellent service and attention to detail. I would highly recommend purchasing from etrailer. Prices are great and they have a wide selection of information that helps with the purchase decision. Very impressed.


Seems expensive for what it does but sometime these one-function devices can save you a lot of money. This is my case. My 2003 GMC Sierra doesn't fall into any category on this website -- at least I couldn't find any good info -- it's somewhere between 2002 and 2004 as far as towing package is concerned. This device allowed me to figure it all out.


This circuit tester was worth every penny. The audio and light indicators took all the guesswork out of the wiring. It made it easy to identify turn signal and brake wires and I was able to test for proper functionality in my trailer contact once everything was installed. Highly recommended.


I have placed several orders with e-trailer over time and keep returning. I have gotten ffast response on questions and all orders have been filled correctly an on time.


This really is the ultimate circuit tester!
The audible feature is a huge benefit when working alone and energizing a circuit remotely.... saved me multiple trips between truck cab and trailer tail lights! When working on trailer light circuits, this is a must have tool!


Purchased this to troubleshoot existing truck wiring and wiring I installed. Much more convenient than using my volt-ohm meter (VOM).


Well made, clear instructions and very useful for sorting out trailer wires. If you have several trailers and multiple towing vehicles this is real handy!


Easy to use voltage indicator. Flashes and beeps so you hear and see . Made the job so much easier. The coiled cord is really long and makes it very convenient.


worked great for the purpose check wiring on trailer


High quality equipment! Thanks for the excellent service.


Excellent quality circuit tester. Can check battery drainage and troubleshoot wiring shorts.


This tester is well made and definitely worth the money. Makes troubleshooting wiring problems a breeze.


Very nice tester. Heavier duty than the cheap ones you buy at local retail stores. I like the fact that it also has the audible tone along with the light.


Product were just explained. always a great job. i enjoy doing business with etrailer.


Great product

Great product
Kej263 - 05/04/2018




Looks good


Great tester


Ask the Experts about this Draw-Tite Electrical Tools

  • Troubleshooting Wiring on a 2015 Nissan NV3500 with Factory Tow Package
    I can help you troubleshoot your issue on your 2015 Nissan NV3500. First let me answer your question about the use of a converter. You will not need the use of a converter for the utility trailer, because the 7-way on the vehicle is already converted for use with all trailers. The first thing I would do is use a circuit tester like # 40376 to test the functions on the 7-way and compare them to the 7-way diagram I've linked right here for your convenience. If all the functions are the...
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  • Troubleshooting Aluminum Snowmobile Trailer Where Lights Stop Working When Brake Applied
    For an aluminum trailer with a pivot like yours you will need to run individual ground wires for each light back to the main ground wire of the trailer connector. For an aluminum trailer the ground wire does not typically run to the frame since aluminum doesn't conduct well. Getting the grounds of each light run back to the connector should fix the problem as it sounds like a textbook insufficient ground scenario.
    view full answer...
  • No Power At Vehicle Connector And Trailer Battery Not Charging With Truck Running On Dodge Ram
    I would use a circuit tester, like part # 40376, to check the 7-Way on your Dodge truck. As you look at the 7-Way on the truck, the pin in the 1:00 position is the 12V power supply. This should be hot when the truck key is in the ON position. If it is indeed hot, then you have a problem with the trailer, most likely a dead battery or a bad ground connection. It could also be that the trailer connector is wired for power on the center pin, which would actually be the reverse circuit on the...
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  • Testing a Brake Controller and Trailer Wiring for a Trailer with the Brakes Not Working
    The way the brake signal gets to the trailer brakes is from the controller to the 7-Way, through the breakaway system, and then to the brakes. Since the breakaway system wire is broken that could very well be your problem so I would check that first. To check the brake controller, sever the blue wire a few inches back from the controller. Use a circuit tester like # 40376 that you referenced to test the end of the blue wire coming out of the controller. It should show power on that blue...
    view full answer...
  • Trailer Brakes Do Not Work when Using Brake Controller But Do With a Car Battery
    With a total of 4 brake assemblies, the brake controller power wire will need to be connected to at least a 20 amp circuit breaker and then to the battery. If it is on a lower capacity breaker or fused power source then the draw of the magnets could be too great and cause the brakes not to work. When connected directly to the battery the brakes can draw as much amperage as the battery is rated for. If there is any sort of short, corrosion, a bare wire touching metal somewhere, that is...
    view full answer...
  • Trailer Brake Controller on 2002 Chevy Silverado Does Not Work with Brake Pedal but Does with Manual
    There are a few possible reasons why the brake controller is not working when you step on the brake pedal. First, if it was working before but now it is not then the most likely cause is a blown stoplight or CHMSL fuse. Use the legend on the power distribution box lid to find the fuse locations and replace as needed. You will also want to make sure that the connector that plugs into the port on the truck is pinned correctly. Basically, the wires coming out of the back of this plug should...
    view full answer...
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  • Troubleshooting Brake Controller that Work Intermittently with Brake Pedal, Always With Override
    It sounds like you have a wiring issue on the brake switch circuit and it is making intermittent contact and that explains why it works occasionally. Since the manual override lever still works the rest of the circuits seem to be good. I would recommend you check the brake switch wire for any signs of a short such as exposed or cut wire and fix as necessary. I attached an FAQ on brake controller troubleshooting for you to check out also.
    view full answer...
  • Troubleshooting Trailer Brakes Locking up when Trailer Connector is Connected to 2005 Toyota Tundra
    It sounds like you have the trailer connector on your 2005 Toyota Tundra or trailer wired incorrectly, or there is a short from the 12 volt accessory circuit to your brake output circuit and that is causing your trailer brakes to lock up. The first thing I would do is check the back of the connectors on your vehicle and your trailer and see if there is any obvious things that could cause the short. Next, I would check that the 7-way on your trailer is wired correctly. Check out the picture...
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  • Finding the Correct Brake Switch Wire on a 1994 GMC C/K Series Truck to Install a Brake Controller
    What you will want to do is test each of those wires with the headlights and turn signals on, one at a time. If one of the wires shows power with the headlights or turn signals on then it is not the correct wire. You need the one that is hot only with the brake pressed and not with the headlights or turn signals on. In the event that neither of those wires is correct and you cannot find one that is at the brake switch, then you can find the stop light or CHMSL fuse and tap into it to connect...
    view full answer...
  • After Replacing Trailer Side Connector the Trailer Brakes Stopped Working
    It is possible that in the process of installing the new trailer side connector that a ground connection got knocked loose or something may not be wired correctly. This is common because if you try to install a new connector color for color on the old harness, they may not match up. You have to go by function. On a 7-Way, the brake output pin if looking at the back of the connector where the wires attach, is located in the 5:00 position. That is the power wire for the brake magnets. Make...
    view full answer...
  • Trailer Brake Controller Shows Voltage on Blue Wire without Brake Pedal Pressed
    If the blue output wire is showing power when it should not be then that indicates that the controller is bad and will need to be replaced. But to test it properly you will need to sever the blue wire a few inches from the back of the controller. Then use your tester on the end coming out of the brake controller. If it shows power without the manual override or brake pedal being pressed then the control is bad and will need to be replaced. If it works like it is supposed to then there...
    view full answer...
  • Trailer Brake Controller Shows Constant 12 Volt Power After Wires Corroded and Blew Fuse
    You could have a bad controller or the original short that blew the fuse also damaged the controller. And you could also have another short or not totally fixed the original issue. To test the controller, cut the blue wire a few inches back from the controller. Then use your tester to test the end coming out of the controller. If it shows power without the brake or manual override then it is a bad controller and it will need to be replaced. Also check where the original problem occurred....
    view full answer...
  • Troubleshooting New Brake Assemblies that Do Not Seem to Work but have Voltage to the Assembly
    It sounds like you need to do the initial brake adjustment on the new brake assemblies of your trailer. To adjust the brake shoes, you would access the brake adjuster from the back of the assembly, and adjust it out until you can no longer turn the trailer wheels by hand. Then, back off about 10 clicks for the optimum placement. You can view a video on brake assembly installation and adjustment at the link provided.
    view full answer...
  • After Installing New Trailer Brakes, Front Axle Brakes Work, Rear Axle Brakes Do Not
    I will be happy to help. Since we know the front axle is getting power use your circuit tester and find the wires on the brake magnets for the rear axle to test them. There should be 2 wires. One is ground and the other is the power wire. The ground wire should be attached to a clean and corrosion free bare metal surface near by. If there is no power going to the magnet then there is a wiring issue somewhere forward of them that will need to be addressed. Because the power for the brake...
    view full answer...
  • Brake Controller in a 2001 Dodge Ram Pickup does not Recognize the Trailer
    All of the symptoms you are describing lead me to believe there is a ground problem somewhere, even on the trailer. A weak ground connection can show up with some trucks and not others, we have seen it before. The first step I would take is to inspect all of the ground connections on your truck and your trailer. Inspect the grounds for the trailer connectors and the grounds at the brake assemblies for the brake magnets. Even if the grounds look good, I remove and clean them. If they look...
    view full answer...
  • Finding the Cold Side of Brake Switch Wire on a 1994 Dodge Dakota
    The brake switch wire is potentially a white wire. Start testing with the white wire. You can use a circuit tester like # 40376 if you do not already have a tester. You need the wire that only shows power with the brake pedal and not with the turn signals or headlights. If you cannot find the proper wire then check the truck owners manual for the stop light or CHMSL fuse location. You could then use a fuse tap to get he dedicated brake light signal.
    view full answer...
  • Fixing Lights on a Utility Trailer
    The first thing to do is determine whether the problem is on the tow vehicle or the trailer. You can do this by using a circuit tester, like part # 40376, on the trailer connector and testing the pin for the running lights while the headlights are on. If you get current on that circuit, then the problem exists on the trailer. You will have to trace the running light circuit usually the brown wire from the connector back to the lamps, looking for pinched or broken wires, and loose or missing...
    view full answer...
  • Locating Stop Light Circuit Wire for Brake Controller Install on a 1999 GMC Yukon
    The easiest way to do this is to access the main vehicle wiring harness located under the dash near the steering column. Using a circuit tester like part # 40376, you would probe the wires in this harness until you find the one that only shows current when the brake pedal is pressed. Once you find the right wire, you can tap the red wire from the brake controller into it.
    view full answer...
  • Finding the Reverse Light Wire on a 1995 Ford F-150 for Installing a 7-Way
    Without a tow package, there probably will not be a harness or wire bundle that you can tap into. Your best bet would be to tap into the wiring behind one of your back up lights. Use a circuit tester, like part # 40376, to verify this connection. It sounds as if you have the rest all figured out. Good job!
    view full answer...
  • Trailer Signal and Brake Lights Not Working on a Trailer Behind a 2007 Nissan Titan
    The first thing I would recommend you do is use a circuit tester, like part # 40376, and check your trailer connector on the bumper of your truck. Activate the turn signals and check the appropriate pins for a signal. Then have a helper step on the brake pedal and test for a signal at the 2 pins for the left and right turn signal. If you do not show a signal for any of these functions, you probably have a blown fuse. Consult the vehicle owner manual for the location of the fuses that...
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  • Find the Cold Side Wire for a Brake Light Switch on a 2001 Chevrolet Blazer S-10
    The switch itself is located at the top of the brake pedal. If you cannot access the wires coming off of it, you can access them through the main wiring harness, located under the steering wheel. You will be looking for the thick bundle of wires. Using a circuit tester, like part # 40376, locate the wire that only shows current when the brake pedal is pressed.
    view full answer...
  • Brake and Turn Signals Not Working on a Trailer Behind a 2005 Jeep Grand Cherokee
    I would recommend you use a circuit tester, like part # 40376, and test the pins on the 4 pole while each function is activated. This will narrow down the problem to the vehicle or the trailer. If it works properly, then the problem is on the trailer and vice versa. Closely examine the pins and sockets on each side of the vehicle/ trailer connection, look for any corrosion, which will show up as a green discoloration. Many times, this corrosion will be enough to prevent a proper connection....
    view full answer...
  • Which Wire is the Stop Light Wire on a 2007 Dodge Sprinter
    Due to the varying wire colors between manufacturers and model years, I do not have any information on the specific wire color. The wire you need to tap into will attach to the cold side of the brake switch. The brake switch is located at the top of the brake pedal. We recommend using a circuit tester, like part # 40376, to probe the wires coming off of the brake switch until one is found that only shows current when the brake is pressed. This will be the wire you need to tap the red brake...
    view full answer...
  • Hardwiring a Brake Controller on a 2005 Ford F-250
    At this point, the easiest thing to do would be to install the brake controller as if the vehicle was not wired. The four leads coming off the brake controller are wired as follows: The red wire would tap into the wire coming off the cold side of the brake switch located above the brake pedal. The easiest way to locate this wire is to use a circuit tester, like part # 40376, and locate the wire that only shows current when the brake pedal is pressed. The black wire would run to a 12...
    view full answer...

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