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Hopkins Tow Doctor Vehicle End Test Unit

Hopkins Tow Doctor Vehicle End Test Unit

Item # HM50918
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  • Reviews (6)
  • Q & A (0)
  • Videos (2)
  • Photos
  • Why etrailer?

Hopkins Electrical Tools - HM50918

  • Testers
  • Tow Function Tester
  • Hopkins

  • Allows one person to check that a vehicle wiring harness has been installed properly and all functions are working
  • Tests all tow vehicle functions: ground, auxiliary power, brake, direction, and backup
  • Heavy-duty, 20' extension cord included
  • Adapts to 4-Flat, 6-Pole Round, or 7-way Blade

50918 Hopkins Tow Doctor Vehicle End Test Unit

50918 Hopkins Tow Doctor Vehicle End Test Unit

California residents: click here

Video of Hopkins Tow Doctor Vehicle End Test Unit

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

Video Transcript for Hopkins Wiring - Tools for Wiring - HM50918 Review

Today we're going to be taking a look at part number HM50918 this is the Hopkins Tow Doctor vehicle end test unit. This is going to allow one person to check that a vehicle wiring harness has been installed properly and that all functions are working as they should. It's going to test all tow vehicle functions, so you're going to have the ground, tail lights, left turning brake, right turning brake, backup lights, electric brakes, and your auxiliary power. It's going to come with a really nice storage case. It's got the handle on it. It snaps shut, too. A good storage option there as well as a transportation case if you ever need to move it from one place to the other.

We're going to go ahead and pull everything out here just so we can go over all the different pieces that it comes with. They're going to include a nice little terminal grease packet right here. This is going to be applied to your connection points. That's designed to prevent corrosion from settling into your connections so they include that little packet. This is going to be your head unit, self contained, it's going to feed off the vehicle battery power so you do not have to install batteries in this. You don't have to charge it or anything like that, it's going to be ready to use as soon as it's connected.

It's going to also feature the heavy duty 20 foot extension cord. This is included, that way you can make your connection at the back of the vehicle and you can operate this from the driver's seat as you operate each function. It's going to come with three adapters. You're going to get your four flat style connector. You're going to get your six pole round style connector and you're going to get your seven way blade style connector. Each adapter is going to measure about one foot long and it's going to have the connector on each end.

Here on the head unit, this is going to feature seven LED indicator lights. They're easy to see and each one is labeled, so it's very easy to read. It's got the nice swivel hook up here so you can hook that and hang it if you choose. The Tow doctor has been equipped with resisters that are going to simulate the load that a trailer would put on the vehicles wiring system. The unit's very, very easy to use. All you have to do is select the proper adapter that's going to work with your connect.

For instance, today I have a four way flat connector hooked up that way we can see how this thing operates. I would take the cord from the head unit, plug it in to the cord of my adapter. Make sure pushed in there all the way and once I have that connected, I'll take my four way flat connector, plug these two in. I already have power running so you can see that my tail lights are going to be lit up, letting me know that it's wired correctly and that it's working all right. With everything connected properly, what we can do is we can apply each function individually and this unit will tell us whether or not everything is wired correctly and if all the functions are working. I'll call it out if you just keep an eye on that. What I'm going to do is I'm going to go ahead and apply my left turning brake signal and you can see how that light lights up when I apply my brakes and when I apply my turn signal. We'll go ahead and do that for our right turning brakes. See there, it lights up. Turn signal. Then we'll go ahead and apply both of those and they'll light up at the same time. That just gives you an idea of how this would work. Now that we've gone over the functions and we see how it would operate, that's going to do it for today's look at part number HM50918. This is the Hopkins Tow Doctor vehicle end test unit. .

Customer Reviews

Hopkins Tow Doctor Vehicle End Test Unit - HM50918

Average Customer Rating:  5.0 out of 5 stars   (6 Customer Reviews)

- HM50918

Works well to let you know if you've wired or are wired correctly. Big time saver. No more hours tracking down what the problem is. This device tells you when a circuit has no connection.

- HM50918

Bought this item and also the trailer circuit tester. Both work great and save tons of time checking lights and brakes for the company fleet.

- HM50918

I have 4 trucks that tow trailers everyday, we have been trouble shooting the wiring for months. This tool has made solving all my electrical problems so easy! Great tool Bruce

- HM50918

Nice tool for testing trailer wiring.

- HM50918

Good tool. Fast shipping.

- HM50918

So far so good. Just received the package today.


Ask the Experts about this Hopkins Electrical Tools

  • Troubleshooting Electric Over Hydraulic Brakes that Do Not Apply
    If the brake controller appears to working properly and the brakes of your electric over hydraulic setup are still not applying that would lead me to believe that the problem is on the actuator itself. Does the actuator cycle on to build pressure when you connect it to your tow vehicle and the vehicle is turned on? If not, then the problem may be that the actuator is not getting the 12 volts it needs to power the unit. Typically, the 7-way of the trailer wiring powers the actuator through...
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  • Does Blinker Light of Hopkins Tow Doctor Tester # HM50918 Flash with Blinkers
    When you use the Hopkins Tow Doctor Vehicle End Test Unit # HM50918 to test the blinker functions the light on the display of the unit will blink with the blinker. If you check out the 1:20 mark of the video I attached you'll the red lights blinking when the blinkers are applied.
    view full answer...
  • Does the Tow Doctor Trailer Side Tester Work on a Trailer with LED Lights
    The Tow Doctor for the trailer side is # HM50928. The other one, # HM50918, is the vehicle side. For the trailer side model it does not work if the trailer has LED lights. LED lights draw too little power for the tester to work properly. You could test the trailer side by using a separate 12 volt wire and applying power to each function. If the function does not work doing this test you know there is a wiring issue.
    view full answer...
  • Wiring Tester Kit for Both Vehicle Side and Trailer Side Connectors
    I do have options for you but we do not have an all inclusive tester kit that will test flat and round trailer connectors on both the trailer and vehicle. Instead you will want to use part # HM50928 for the trailer end and part # HM50918 for the vehicle end. Both kits have the ability to test 4-flat, 6-round, and 7-way connectors. I have attached a review video on both the vehicle side and trailer side tester kit for you as well.
    view full answer...
  • Electric Trailer Brake Light Does Not Light Up When Testing with a Hopkins Tow Doctor Tester
    The replacement unit, # 4010509028 is a replacement for Tow Doctor part # HM50928. It looks like the Tow Doctor version you ordered is # HM50918. The difference is the HM50928 has more features. To test the brake controller output someone will need to sit in the truck and apply the manual override so that it is sending power back to the trailer connector. Otherwise, what will happen is what you are seeing, a slight flicker of light. That is the brake controller checking to see if a trailer...
    view full answer...
  • Circuit Tester Needed for 7-Way on 2018 Chevy Colorado
    All of the circuit testers we carry, like the Tekonsha # 6562, are universal fits for vehicle connectors which is why these products aren't listed in our fitguide. The note on the product page about the Ford OEM brake controllers has more to do with the actual brake controller than the vehicle itself. If the notch on your 2018 Chevy Colorado is facing down then none of the other 7-Way testers like this will work and you either need to use a single prong tester like part # PTW2979 to test...
    view full answer...
  • How to Bypass 12 Volt Trailer Wiring Accessory Circuit Not Functioning on New Ford Truck
    It would not as it's only really designed to see if voltage is present. The new Ford trucks need a specific amount of load on the circuits to activate the 12 volt circuit which is pretty annoying. If you are looking for a way to bypass that let me know as we can help.
    view full answer...
  • Comprehensive Vehicle Side Trailer Connector and Wiring Tester
    Most of the vehicle end trailer connectors we have will test for voltage on the circuits. If there was a short to ground then all of the lights would light up on the tester and you would know there is a problem. We do have a comprehensive trailer side tester, # 8010, which goes much further than any of the regular testers like # I26. But it is not designed for the vehicle side. For the vehicle side we have # HM50918 that can test multiple connector types on a vehicle (4-Flat, 6-Way round,...
    view full answer...
  • Rubber Bumper for Stock Trailer
    We do have some rubber bumpers for you to install on your stock trailer. They are all 96" long so it just depends on what kind of width you're looking for: 96" Long x 2-1/16" Wide - # D2-96 96" Long x 3" Wide - # D3-96 96" Long x 4" Wide - # D4-96 These come pre-dilled with holes every 11" but you can cut these to length and drill new holes to match your application if you need to. Attached is a review video for you to check out.
    view full answer...

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Info for this part was:

Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Jacob T
Video Edited:
Jacob T
Employee Dustin K
Video by:
Dustin K
Employee Cole B
Installed by:
Cole B
Employee Hayden R
Installed by:
Hayden R
Employee Wilson B
Updated by:
Wilson B
Employee Alexander C
Updated by:
Alexander C

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