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Universal Wiring Harness for Hopkins Multi-Tow Vehicle-End Trailer Connectors - 4' Long

Universal Wiring Harness for Hopkins Multi-Tow Vehicle-End Trailer Connectors - 4' Long

Item # HM40985
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HM40985 - 7 Blade Hopkins Wiring
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This 4' long universal harness can be hardwired into your tow vehicle's wiring system so that you can install Hopkins Multi-Tow connector 40965 or HM40975 (sold separately). Harness plugs directly into the Multi-Tow connector. Call 800-298-8924 to order Hopkins accessories and parts part number HM40985 or order online at etrailer.com. Free expert support on all Hopkins products. Guaranteed Lowest Price and Fastest Shipping for Universal Wiring Harness for Hopkins Multi-Tow Vehicle-End Trailer Connectors - 4' Long. Accessories and Parts reviews from real customers.
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  • Reviews (11)
  • Q & A (21)
  • Videos (3)
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Hopkins Accessories and Parts - HM40985

  • Wiring
  • Vehicle Wiring Harness
  • Hopkins
  • 7 Blade
  • Universal

This 4' long universal harness can be hardwired into your tow vehicle's wiring system so that you can install Hopkins Multi-Tow connector 40965 or HM40975 (sold separately). Harness plugs directly into the Multi-Tow connector.


  • Lets you install a Hopkins Multi-Tow connector (sold separately) on any vehicle
  • Works with HM40940 (7-way), 40965 (6-way and 4-way) or HM40975 (7-way and 4-way)
  • Hardwires into your tow vehicle's wiring system
  • Plugs directly into your Multi-Tow connector


  • Wiring configuration:
    • Green: right turn signal
    • Yellow: left turn signal
    • White: ground
    • Brown: tail lights and side marker lights
    • Blue: electric brake
    • Red: auxiliary power
    • Purple: backup/reverse lights
  • Length: 4'
  • 90-Day limited warranty

40985 Universal Wiring Harness for Hopkins Multi-Tow Vehicle-End Trailer Connectors 40965 and HM40975 - 48" Long

Installation Details HM40985 Installation instructions

California residents: click here

Video of Universal Wiring Harness for Hopkins Multi-Tow Vehicle-End Trailer Connectors - 4' Long

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

Video Transcript for Trailer Wiring Harness Installation - 2002 Chevrolet Silverado

Speaker 1: Today the 2002 Chevrolet Silverado. We're going to review and install the universal wire harness, the Hopkins Multi-Tow vehicle and trailer connectors, part number HM40985.This is the connection point right here that goes behind your seven-fold connector. This is what's called the US car connector style. The cord has got a four-foot length to it and has provisions for all seven circuits. You've got ground, 12-volt power, brake controller output, left turn, right turn, run light circuit, and reverse lights. It also comes with a variety of butt connectors to suit different gauge of wires.

Up here larger wires. You're going to use the yellow ones. And for smaller wires, you're going to use the blue ones.These will work fine and do the function, but however for longevity, when I install this I'm actually going to replace these with some featuring butt connectors that are more suited for outdoor use. For larger diameter wires, I'm going to use part number DW05745-5. For my smaller wires, I'll use part number DW05744-5.

It also comes with a small vial of dielectric grease. I kind of like to put that around the connection right here to help protect the connection points from corrosion over the long term.A good reason to install this on your truck is a lot of times in older vehicles and trucks, if you run into situation where your wires are damaged . yeah, they had some minor repairs with some butt connectors and what not; however you can fix that just fine. But if something more worse happens such as the wire that goes into your connector, the US car connector, sometimes they just break right on the inside and you can't do nothing about it so you have to replace the whole assembly.Now, to remove this from our seven-fold connector, simply push down this tab right here. It may help to spray it down with some soapy water or even some lubricant to help pull apart, but push it in a little bit it helps.

Then this tab. You may also have a little gray locking tab. It just slide back out of the way to make it work, too. Push down on that center and pull it apart.We'll cut the wires to an even length one at a time. Take a moment and strip back the wires maybe about a little over a quarter inch maybe.

Wire stripped. You've got to get it to compress the wires by twisting them. Take a butt connector and a crimp tool. For our smaller wires, we're using a blue butt connectors. Make sure they're crimped. Give them a quick test. Now for our final three wires, we'll use our yellow butt connectors.Now, let's get our Hopkins part ready to go. I am going to remove this ring terminal here to hook that up to the factory ground wire, which is a white one on our truck. I'm just going to even these guys out and re-strip them.Onto connecting our wires, we're going to go white to white and pretty much match up color for color from here on out. Now, we've connected our wires color for color as you can see; however, there's a dark green and a light green. Dark green's going to be your turn signal, so that's going to go to your green on our Hopkins part. Now, there's a light green here. This is for reverse light. That's where color's going to change because purple on our Hopkins part. So we'll connect those two together just like we did before.We'll have an extra wire here for a third brake light which is commonly used on a camper shell. In our case there's no provision for it nor we need it, so we're just going to leave a butt connector for future use and we'll just leave it alone for now.Let's apply some heat to our heat shrink butt connectors. Always use a device like this to make your connections and shrink them up. If you can't do that with open flame. It's really easy with a lighter to over cook it and you'll get bubbles in your plastic here, and that's no good and it will cause it to deteriorate rather fast. We use some electrical tape, bundle them all together to make it nice and neat.We'll break out the dielectric grease here, just put it on the electrical connections right here. Just on the metal parts is all we need. Then we'll push this onto our factory connector. Align up the key way and then slowly but firmly push it in. You may or may not hear a click, and then give a tug back to make sure it's engaged.Zip ties will be needed because it does not come with our Hopkins part. We'll use it to bundle it up and keep it safe and out of the way. Then we'll cut off the tails.Now is the time to go ahead and try it out and test it. You at home will probably use a test light or just just your trailer to make sure everything works. I don't have a trailer handy so I'm going to use one of my testers from my shop. First off, we have a running light circuit, our left turn signal, our right turn signal. Let's check our brake signal, which we should have a constant output on the left and right turn. Okay. Now we'll try our brake controller, make sure to output there. And we'll also look for a reverse light circuit. Finally, we'll double check for our 12-volt power that goes out to our trailer for various accessories. And we've got battery power there.And with that, that will finish it for a universal wiring harness for Hopkins Multi-Tow vehicle and trailer connectors. Part number HM40985 on this 2002 Chevrolet Silverado.

Customer Reviews

Universal Wiring Harness for Hopkins Multi-Tow Vehicle-End Trailer Connectors - 4' Long - HM40985

Average Customer Rating:  5.0 out of 5 stars   (11 Customer Reviews)

This 4' long universal harness can be hardwired into your tow vehicle's wiring system so that you can install Hopkins Multi-Tow connector 40965 or HM40975 (sold separately). Harness plugs directly into the Multi-Tow connector.

- HM40985

Worked great! 938693

- HM40985

Perfect fit with the HM40975 4pin/7pin connector. Wiring was correct - both position and color of wire. I didn't need the full 7-pins - I just cut the pigtail to length, clipped off the red, blue, and purple wires, and attached a 4pin connector to the other end. 831292

- HM40985

Product fit perfect and arrived fast. T hanks 819427

- HM40985

As advertised, great product 511276

- HM40985

Worked as it was designed for. 486904

- HM40985

Ok, I just found a package from you guys on my porch when I got home. I'd gotten an email today that said it'd been delivered, but I KNEW that was a mistake because I'd just ordered a couple days ago, paid ZERO for standard shipping, so was certain there was no way anything got here already. Get home, it's ALL there!!!!! It's all exactly what I ordered, and I'll be providing reviews of the stuff as I get it installed and used. But as for etrailer? Nothing but awesome!!!!!!!!! Amazing job. Now THAT'S customer service! 483260

- HM40985

Very easy to install. Worked great with the trailer connector hm40975 I bought from you. Very good instructions 398752

- HM40985

I can't begin to say how pleased I am with the model 50002 backup camera system: https://www.etrailer.com/Backup-Cameras-and-Alarms/Hopkins/HM50002.html My 2003 Toyota Tacoma has a factory installed 4 wire system, however, I I needed the 7 wire connector to use with the backup camera. I emailed support and they quickly sent a reply with a link to instructions. It was an easy project - I had the wire conversion and the backup camera installed in less than 2 hours. I love the backup camera with the variable warnings as you approach obstacles and it works great for hooking up my trailer unassisted. 5 stars on both items - for sure! 277673

Great! I love it, cant imagine being without it. The backup obstacle warning system is terrific - very accurate and lining up my trailer by myself couldnt be easier.
David H - 07/30/2017


- HM40985

Excellent fit 274527

- HM40985

Exactly what I was looking for. 268862

- HM40985

great product. 184184


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Info for this part was:

Test Fit:
Joe V
Test Fit:
Shane T
Test Fit:
Shane H
Written by:
Tyler C
Expert Research:
Michael H
Expert Research:
Jameson C
Expert Research:
Adam R
Installed by:
Jeff D
Video Edited:
Jacob T
Video Edited:
Dustin K
Updated by:
Sarah W
Updated by:
Alexander C
Video by:
Jonathan Y

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