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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.


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


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!


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

  • Horse Trailer Turn Signals and Running Lights Not Functioning
    You can immediately test the relay theory by simply pulling the suspect relay and replacing it with one of the others on the fuse block. If this solves the problem, replace the relay and you are good to go. You will want to consult the owners manual regarding the location of the fuses that protect the towing circuits on your vehicle. Make sure these fuses are not blown. Next, use a circuit tester, such as part # 40376 and test the trailer connector on the vehicle. Have a helper activate...
    view full answer...
  • Trailer Brake Lights Not Functional, But Turn Signals Work
    Is your 7-way factory installed with the tow package, or was it installed aftermarket with a taillight converter? If this is an OEM tow package, the directional and brake lights are combined on the same circuit, if one is not working neither will the other. If you are using an aftermarket taillight converter feeding into your 7-way, you will want to troubleshoot it. Trace the wiring back from the connector and locate the converter box. You will want to use a circuit tester such as part...
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  • Wiring a European Style 7 Pole Connector
    I do not have the full answer, but I have part and can tell you how to figure out the other part. I will send a second email with a diagram, but first I will explain what all you need to do. European style trailers are wired very differently than our trailers here in the U.S. and so since we do not get questions about them, I cannot guarantee I have the answer right. There are 7 round pin poles on a European style connector. At most I can only think of two wires that will need to be doubled...
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  • Brake Stoplight Switch Connection for Brake Controller Install on 2006 Uplander
    I've done some research, and have found that yes, you would want to connect to that white wire coming out of Connector 2, Pin 30. This wire is located in the Body Control Module, which is located above where your left knee would be as you are sitting at the wheel. Use a circuit tester, such as part # 40376 to verify that this white wire goes hot only when the brake pedal is pressed.
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  • Journey HD Brake Controller Showing OC Error Code, No Reaction on Controller When Brake is Applied
    Take a close look at your trailer connector, make sure that its not corroded or damaged. If you can see any green corrosion on the pins, the corrosion might have spread to the interior of the connector, interfering with the connection. The 12 Volt accessory circuit on your 7-way connector uses pin # 4, which would be in the 1 oclock position when you are looking at the front of the connector. The # 3 pin carries the running/marker light signal, and would be in the 11 oclock position. The...
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  • Wiring Installation Instructions for a 2005 BMW X5 with Multiplexed Wiring System
    We have the instructions online on the product page for the Upgraded Heavy Duty Modulite Circuit Protected Vehicle Wiring Harness, item # 119190. I realized the instructions are not linked to the item # 119190KIT, page and have sent an update for this page. There is a wiring diagram at the top of the instructions, see link. You will need a circuit tester, item # 40376 if needed, to check the vehicle wiring behind the taillights to make sure you get the correct trailer lighting functions...
    view full answer...
  • Troubleshooting Trailer Wiring Installation on a 2003 Honda Accord Wiring #118302
    It sounds to me as if you have a problem with the trailer wiring. I would start off checking all of my ground connections and tracing all the trailer wires to be sure none are broken or shorted. The first place I always look is where the license plate mounts with the taillight on the left side of the trailer. The lights are most likely grounded through the mounting connection to the frame and if the bracket is plastic it can sometimes interfere with the connection and cause problems....
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  • Wire Colors for Installing 7-way Connector on 1991 Ford F250
    According to the information I have, the wires serve the following functions. The orange wire with a blue stripe controls the right turn/ brake light. The light green wire with the orange stripe controls the left turn/ brake light, the brown wire carries the signal for the running/ marker lights and the black or gray wire is the ground. The black wire with a pink stripe carries the signal for the reverse lights. This will eliminate 5 wires, leaving 3 remaining. One of the remaining wires...
    view full answer...
  • How to Wire New Trailer Taillights with Two Black and One Red Wire
    Of the three wires, one would be the ground, one for the turn signal/brake light, and the third for the running lights. I am not familiar with the wire colors you describe. Your best bet would be to connect to the existing wires in differing combinations until the lamp works correctly. The first step in diagnosing the wiring problem would be check the wires leading to each fixture to ensure that the signal is getting through. Typically, there will be a yellow and a brown wire on the drivers...
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  • Trails West Horse Trailer with Dome and Spot Lights That are Not Functioning
    The interior lighting and spot lights are typically wired two ways. They are either run off of the running light circuit coming off of the trailer connector, or the circuit that provides 12 volt power to the trailer. You do not mention that the running lights are not functioning on the trailer, so I will assume that they are. If these lights are wired to the running light circuit, the problem most likely exists either at the point where the wires providing power to the malfunctioning lights...
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  • Brake Controller Wire Functions By Wire Color
    The wires exiting the rear of your controller serve the following functions. The blue wires carries the brake output from the controller, the white wire is the ground, the black wire supplies 12 Volt power, and the red wire is tied into the vehicle brake wiring. If the wiring adapter you have is an aftermarket harness, it should wire up color for color. To the right I have attached a picture of a diagram of how brake controllers wire to tow vehicles. To be safe, I would suggest using a...
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    Image 1 for
  • 2006 Wells Cargo Running Lights Stay on When Vehicle is Turned Off
    I have the same truck and do not have the problem you are experiencing. I do not believe it is the factory vehicle wiring that is causing the problem. It sounds like the trailer connector is mis-wired. I would use a circuit tester, item # 40376 if needed to check the connection points in the connector on the vehicle first to make sure that there is not power on the running light circuit when the vehicle and lights are turned off. If not then the vehicle side is eliminated as the problem...
    view full answer...
  • Interior Trailer Lights Not Working with a 2003 Chevrolet Tahoe
    I would start out using a circuit tester, item # 40376, and checking the vehicle end connector. If you have power to the connector you will then need to proceed with checking the trailer connector and trailer wiring. If all of the other lights are working correctly then the problem is realted to the one circuit. The fuse for power to the trailer connector should be under the hood in the electrical center and there should be a diagram showing the fuses, along with a list of what each fuse...
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  • Troubleshooting Brakes that are Locked Up on Trailer
    Trailer brakes are engaged by a magnet that receives power from the brake controller. If the magnet is receiving power when the trailer is connected and the brake pedal is not pressed on the vehicle and the power setting is adjusted properly then there is a wiring situation that needs to be rectified. I would begin by checking the brake feed wire close to the trailer brakes themselves with a circuit tester, item # 40376 if needed, to see if there is power going to the trailer brakes when...
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  • Tail Lights are Not Working on a 1990 Cadillac
    If you are talking about the taillights at the trailer connector you will need to use a circuit tester, item # 40376 if needed, to check the brown wire to the connector and see if there is power on this wire when the taillights are on. If not then there is a problem on the vehicle. If the vehicle taillights are working and there is power to the trailer side of the brown taillight circuit then you need to check the ground connections on the trailer. The most common point that ground is lost...
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  • Brake Controller on a 2002 Chevy Silverado Does Not Work With Brake Pedal Applied
    The manual override switch on your brake controller is operating the brakes, but they are not working when the vehicle brakes are applied, is that correct? If this is the case, with a trailer connected, use a circuit tester, such as part # 40376, on the red wire exiting the rear of the brake controller. Test this wire as the brake pedal is pressed. If you are NOT getting any signal on this wire, you most likely have a blown fuse in the power distribution box located under the hood on the...
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  • Troubleshooting Malfunctioning Tail/Running Lights on a Basic 4-Way Trailer Wiring System
    First thing to check would be the connector at the vehicle. The brown wire is the the tail light/running light circuit. Use a circuit tester, like part # 40376, to make sure that the post with the brown wire on the vehicle connector is getting power when you turn on the head lights. If everything works properly at the connector, then move on to the trailer wiring. The wires on a 4-Way system are as follows: white = ground, brown = tail light, yellow = left side blinker and brake, green...
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  • Troubleshooting Wiring on a Fifth Wheel Trailer With No Tail Light Function
    Your best course of action is going to be a systematic check of the wiring, starting from the front of the truck to the rear of the trailer. It will take some time, but you will find the problem this way. I suspect the problem is on the trailer, most likely somewhere between the side markers and the tail lights. However, the vehicle can be checked quickly and if the problem is there it could save a lot of time Start at the front of the vehicle by checking fuses. Your vehicle owner manual...
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  • Checking 7-Way and 6-Way Connector for Proper Wiring
    The method of wiring a 7-way blade-type trailer connector is standardized. I would recommend using a circuit tester, such as part # 40376 on the 7-way to ensure that it has been wired correctly. Test each pin as its function is activated. If you were to look at the front of the connector, and compare the pins to the face of a clock, the 12-volt accessory pin would be at the 1 position, the right turn in the 3 position, the brake controller output at 5, ground at 7, left turn at 9, and running...
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  • Troubleshooting Brake Output Pin on 7-Way Connector Putting out Constant 12-Volts
    I am guessing that either your trailer connector is wired incorrectly or there is a problem with your brake controller. The only pin on the connector that should show constant voltage is the 12-volt accessory circuit. The pin for the brake output should only show output when the vehicle brakes are applied or the override switch on the brake controller is activated. If you are getting constant 12-volt output on the 7-way connector, I would first recommend checking that the connector is...
    view full answer...
  • Trailer Running Lights Not Working On a 3500 Dodge Ram Pickup
    There should be two fuses in the electrical panel under the hood of your Dodge Pickup for the trailer wiring. Check those again and you may find that is the problem. If all of the fuses are good then I would use a circuit tester, item # 40376, to test the taillight connection in the trailer connector on the vehicle. This connection point, for running lights, should be in the 11:00 position in the trailer connector. If you have power there then the problem is with the trailer. If you do...
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  • Will Bully Ball Mount Hitch Backup Lights Work on a 2006 Chevy Tahoe and How to Install
    The fixture slips over a ball mount and uses a set screw to stay in place. This kit does not connect to a standard 4-Way wiring connector as a 4-Way does not have a signal for reverse lights. You would have to wire the kit as shown in the video. The wiring kit in the video comes with 3 wire leads. The first is the black wire with the ring terminal. This is the ground wire that needs to be attached to the vehicle body or frame. Next, the white wire, needs to be connected to the vehicle...
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  • Troubleshooting Intermittent Running Lights On a Trailer with 4-Way Connector
    The first things I would check are the ground connections on the trailer. The connection of the trailer lights to the frame is especially suspect if the lights get their ground through the mounting hardware. If all of your ground connections are good and this does not solve the problem I would next test the Modulite converter. Use a circuit tester, item # 40376 if needed, and check the wiring on the vehicle side of the converter. You should have power for each function, yellow/left turn,...
    view full answer...
  • Utility Trailer Brake Lights Not Working When Headlights are On, on a 2004 Chevrolet Trailblazer
    It sounds to me like you have a bad ground on the trailer. You will need to make sure the white wire from the 4-Way connector on your trailer is grounded properly and then check all of the ground connections on the trailer especially where the taillights are mounted to the trailer frame. Also if the light brackets are bolted to the trailer check to be sure they are making good ground contact to the trailer frame. If a plastic license plate holder is mounted between the left side taillight...
    view full answer...

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