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Circuit Tester Kit

Circuit Tester Kit

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Electrical Tools 40376 - Circuit Tester - Draw-Tite
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  • Reviews (24)
  • Q & A (0)
  • Videos (2)
  • Photos
  • Why etrailer?

Draw-Tite Electrical Tools

  • 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

Item # 40376

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   (24 Customer Reviews)

Circuit Tester Kit


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


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


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.


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


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!


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 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.


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.


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.


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


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


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


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





Looks good


Great tester


See what our Experts say about this Draw-Tite Electrical Tools

  • No Numbers Display on Prodigy Brake Controller when Setting Up the Controller
    It sounds like there could be a problem with the brake controller or the connections going to it. The first thing you will want to check is to make sure the controller is getting power. Use a circuit tester such as # 40376 to test the black wire going into the controller. If it does not have 12 volt power then that would be the problem. There are different things that can occur that would make this happen. If you happen to have a Chevy/GMC truck or SUV then it is likely that you will need...
    view full answer...
  • Trailer Lights Work on One Trailer but Not on Three Other Trailers Towed by 1998 Toyota Tacoma
    It sounds like a problem with the ground or wiring on the trailers, but it would be wise to check all of the components in your wiring system. You can test the trailer connectors on the 1998 Toyota Tacoma and the trailers with a circuit tester like part # 40376. I am including a link to a FAQ page on trailer wiring that will show you the functions of each pin on your connector, depending on if it is either a 4-Way, 5-Way, 6-Way, or 7-Way. This will help you determine if there is a problem...
    view full answer...
  • Prodigy Brake Controller Flashes SH After Moving it from One Car to Another
    The circuit breaker would reset so the power would be interrupted and you wouldn't see a display during that time so I don't think it is the circuit breaker. The white ground wire, if hardwiring in the controller, should go to the negative battery terminal. It needs a substantial ground and that is the best place to get it. The SH is indicating a short circuit It could be the red wire. On a brake switch there can be more than 1 wire that shows power with the brake pedal. If the wire shows...
    view full answer...
  • Troubleshooting Draw-Tite Activator ll Brake Controller On 2002 GMC Sierra
    Since you said the trailer lights work great on other vehicles that helps narrow down the probable cause of the problems you are having. There is some testing you can do. In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester like part # 40376 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override or brake pedal. If it shows power at idle then there...
    view full answer...
  • Electric Trailer Brakes Make Noise But Will Not Engage
    The first thing you will want to check is the output voltage on the brake controller. If it is set too low it will not send enough power back to engage the trailer brakes. For testing purposes it is easiest to set it to full power. Using a meter or circuit tester like # 40376 make sure that power is getting back to the trailer connector, which it does sound like it is. Then with the trailer connected make sure power is getting to the brake magnets which again it sounds like it is. That...
    view full answer...
  • Troubleshooting Electric Brakes Not Working on Dual Axle Box Trailer
    In order to determine why the brakes aren't working on your dual axle trailer, I recommend first cutting the blue wire 5-6 inches behind the controller and use a circuit tester like part # 40376, to verify that power is present. Power should be present when the manual override control is used. If no power is present, the brake controller may be malfunctioning and require replacement. The next step would be to test the 7-way on your tow vehicle. Using a circuit tester, verify that power...
    view full answer...
  • Trailer Right Turn Signal Problems with a 2006 Chevy Silverado
    First thing I would do is disconnect the trailer from your 2006 Chevy Silverado so you can check the vehicle side connector with a circuit tester like # 40376. Test the right turn/brake signal. You should experience the same issue here since it sounds like you've isolated the issue to the truck and not the trailer. Make sure the connector is clean and free of any dirt or corrosion. Using a wire brush should suffice. If the wires behind the connector are frayed, cut them off at the damaged...
    view full answer...
  • Troubleshooting Weak Trailer Brakes on a Toy Hauler Even After New Axles
    This could be a magnet wiring problem. It is unlikely that the magnets are bad on new assemblies, but if the wiring is not properly connected, it could cause problems. Check to see that the magnets are properly grounded to a clean, bare metal surface free of corrosion. A bad ground would not allow the circuit to be complete and lead to the brakes not performing like they should. You can also try running all of the brake grounds back to the main ground of the trailer. The new brake assemblies...
    view full answer...
  • How to Find Wire Functions of 1996 Chevy Pickup Truck Electric Side Mirrors
    CIPA does not provide the wire function schematic for your 1996 Chevy pickup so I am unable to tell you the wire functions. You might be able to figure it out by using a circuit tester such as # 40376. What you would do is plug in your old factory mirror to the wiring harness and then probe each wire with the tester, one at a time, while using the adjustment knob to move the glass up, down, left, and right to determine the functions of the wires. Please note that the only way the electric...
    view full answer...
  • Trailer Brakes Activate Every Time Turn Signal is Used
    It sounds like you wired the brakes into the combined stop/turn signal circuit on the trailer. Trailers use what is called a combined system meaning that the brake lights and turn signals are on the same tire. So when you are using the turn signal the wire is energized and will apply the trailer brakes when the light blinks. To use the electrical trailer brakes you have to have a dedicated wire just for the brakes and you must use a brake controller in the tow vehicle. The most common...
    view full answer...
  • Weak Trailer Brakes On Trailer Towed by Ram 3500 or Chevy 2500
    Which brake controller are you using? What are the years of the trucks? If using factory integrated brake controllers you may need to adjust the gain (same on aftermarket controllers) to increase the output voltage. Trailer brakes work on varying voltages. At 4 to 5 volts that is not quite half of full power. At 12 volts the magnets would be fully energized. Also, where are you testing for voltage? Adjust the power output on the brake controller to the maximum and then have someone fully...
    view full answer...
  • Troubleshooting Trailer Light Wiring with a 2012 Ram 1500 Tow Vehicle
    To determine if the issue is on your 2012 Ram 1500 or the trailer you will need to disconnect the trailer and use a circuit tester such as # 40376 to test the vehicle side connector. With the running lights on, test the pins on the vehicle side connector. If there is no power at the connector then the issue is on the truck. If there is power at the vehicle connector then the issue is on the trailer. You can check to see if the tow package fuses and relays are present or just bad by using...
    view full answer...
  • How Do I Wire Utility Trailer that has 2 Yellow and 2 Green Wires
    My suggestion is to test the wires for function with the trailer connected to the tow vehicle. You will need a circuit tester, like part # 40376 and a 12v power source, like a car battery. You can then probe the connector with the tester to determine the specific functions of the wires. I have included a link to a wiring FAQ that explains the functions, wire colors, and size wire used on various connectors.
    view full answer...
  • Troubleshooting Trailer Wiring When Turn Signal Is Not Working
    One of the most common causes of trailer light failures is the ground. You will want to make sure the ground wire is secured to a clean, bare metal surface and that there are no signs of damage to any of the wires on the trailer. Check the harness connector to make sure it is clean and free of rust and corrosion. If that all checks out on the trailer you will want to check the output from the vehicle with a circuit tester like part # 40376.
    view full answer...
  • No Right Turn Power on Pin 2 on a 10-Way Connector on a 2007 Jeep Commander
    Thanks for sending a diagram! The fuse panels on your 2007 Jeep Commander are located under the hood and on the lower instrument panel just to the left of the steering column. I did some research on your Jeep and fuse location number 21 (rear turn/taillights) in the front underhood fuse box is a 20 amp yellow mini fuse. Replace if blown. I would still take a look at your owners manual to confirm and I think it's page 399. I would also check your 10-pin connector for any corrosion and...
    view full answer...
    Image 1 for
  • Brakes Do Not Work On Trailer After Replacing Wire Harness
    It sounds like you are replaced the wiring harness on your vehicle or on your trailer and still having problems with no brakes. I have attached some helpful articles that explain brake controller installation and troubleshooting you can check out. The problems can run from incorrect harness, wiring, or fuses and relays all the way to the trailer wiring or the brake controller. You will first want to make sure that the wire that leads from the trailer side 7-Way to the trailer brakes is...
    view full answer...
  • While Installing Light Bar Connector Arced and Light Bar Will Not Come On
    It is possible that a fuse is blown. Use the trucks owners manual to find the fuses related to the tow package wiring since it sounds like that might have been what you were plugging or splicing into. There is likely a fuse and/or relay or more than one related to the tow package circuits that you can check. Or if you have a meter or circuit tester such as # 40376 you can test the connector or wires you were tapping into while someone sits in the truck and runs through the lighting functions....
    view full answer...
  • Dome Lights Are Not Working In Enclosed Trailer With 7-Way Connector
    The first thing I recommend is to use a tester like part # 40376 and check the 12V circuit on the wiring connector on the truck. If you have no current showing there may be a fuse missing or blown for that circuit. You would want to check the owner's manual or with your dealership to see which fuse is dedicated to that circuit. There are times when the dome lights may be attached to the running light circuit. You may want to try turning on the truck headlights when the trailer is hooked...
    view full answer...
  • Troubleshooting Trailer With Malfunctioning Brake Lamps Towed By 2015 Chevy Silverado 2500
    It sounds like you've used a circuit tester to check the brake lamp functions on the 7-way on your truck. With the brake pedal applied, you should get a signal both the right and left turn signal pin, as shown in the photo I've provided. If you or a friend have another trailer handy, you might try plugging that in, to see if the lights behave the same way. I'm doubtful it's a fuse, because the tow package on your Silverado combines the signal for the trailer turn signals and brake lamp...
    view full answer...
    Image 1 for
  • Passenger Side Tail Light Wire Functions for a 2001 Chevy Suburban
    It looks like GM is using the black wires as the ground wires since that is the only common wire color on the 3 connectors in your picture. And they all go to a terminal indicated with the letter G which likely stands for ground. It looks like the center and right connectors in the picture have a single function and the one on the far left either has 2 functions or it also has a neutral wire. The easiest way to determine the functions of the wires is to use a circuit tester such as #...
    view full answer...
    Image 1 for
  • Prodigy Brake Controller Shows SH and oL Error Codes on a 2000 GMC Sierra
    The SH error does indicate a short and the oL indicates an overload condition. The first things to check and the easiest are the vehicle and trailer side connectors. Dirt and corrosion can cause this problem. Make sure the vehicle and trailer side connectors are clean and free of corrosion at the pins and in backs where the wires attach. You can test to see if the problem is the brake controller or the wiring somewhere between the controller and the trailer connector. You can test the...
    view full answer...
  • Prodigy Brake Controller Flashing N.C. with a Trailer Connected
    The NC is telling you that the trailer is not connected. Since you are getting this error with the trailer connected, the trailer connector (vehicle or trailer side) might be damaged or corroded, preventing a good connection. Closely examine the pins and sockets on the vehicle and trailer side of the connection. If you notice any green corrosion on the pins and sockets, the corrosion might have spread to the interior of the connector, causing a faulty connection. Cleaning out any corrosion...
    view full answer...
  • After Changing Bearings the Electric Trailer Brakes No Longer Work
    You will want to check the wiring to the magnets to see if something got disconnected when you where replacing the bearings. Make sure that the ground wires are attached to clean and corrosion free bare metal surfaces. Also make sure the power wires to the magnets are not pinched or in need of repair. If the magnets are getting power (which you can check using a circuit tester such as # 40376 while someone activates the manual override on the brake controller) then it could be a different...
    view full answer...
  • Trailer Turn Signals and Brake Lights Not Working with a 2012 Ford F-350
    A lot of Ford trucks use fuses and relays for the tow package wiring. Use the owners manual to locate all of the relays and fuses associated with the tow package wiring. Also, there can be tow package fuses in both the power distribution box under the hood as well as in the in-cab fuse panel. Checking fuses is easy but checking relays can be more difficult. the easiest way to test a relay is to use a known good relay in place of a potential bad one.
    view full answer...

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