How To: Install Heavy-Duty Power Window Harness

Project Overview

Upgrade your power window harness for better power delivery to the window motors for modern day speed and reliability. The heavy-duty harness draws its power from the window switch. Harness has separate relays for up and down functions on both front doors. Comes complete with everything needed to splice into the truck's wiring and works with factory window switches. Installation instructions included.

Project Difficulty
Estimated Parts Cost
Estimated Project Time
2-3 hours
Heavy Duty Power Window Harness

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Required Tools
  • Wire Crimpers
  • Flat & Phillips Screwdrivers
  • Cordless Drill
  • Soldering Equipment
  • Cable Ties
  • Needle Nose Pliers
  • Shrink Tubing
  • Torch
Video Transcription

Hey guys I'm Kevin Tetz, working with LMC Truck to bring you some technical information and how-to videos designed to make your truck project turn out even better.

In this video we're going to address the problem that a lot of older trucks have that are equipped with factory power windows. Check this out... the truck not running and the key on... the window motor it works great until about the midway point and it kind of slows down this has got a brand new lift motor new weather seals everything is lubricated and shipshape and even on the down motion it just seems like the motor is laboring. That's because of the current path going to the switch and then to the motor itself. There's a solution for this problem and it's really slick.

Check it out. This is an LMC Truck exclusive product this is the heavy-duty power window harness and is designed to draw power directly from the battery and put it right to the power window lift motor and eliminate that problem of the slow motor especially in the mid-range motion this has the harnesses that you need a fuse holder all the connectors and terminals that you're going to need including the inline fuse to properly and safely connect your window lift motor directly to the battery.

Now you're only seeing half of the kit here. This is the driver's side, that's because I pre-installed the passenger side. It's essentially the same project the same connections but the driver's side has more lead because it's farther away from the battery in our truck. Now if you tear your door apart and you find yourself needing some parts check out your LMC Truck catalog or go to you'll find everything that you could possibly need to rebuild your door...window regulators, lift motors, switch harnesses, even the bellows between the door and the cab. Everything that you need you can rebuild your truck from the catalog. We may not need everything on the table but it's nice to know that LMC Truck can provide it for you.

Now, let's talk about what kind of tools it’s going to take to do this project. Basic hand tools will get this job done but we are doing a wiring project so you’re going to need the proper tools to crimp wires, cut them properly, strip the sheathing back, as well as shrink tube. Now there are crimp connectors but we're also going to show you some soldering techniques. So you'll need some soldering equipment if you do it the same way that we do. A couple of cable ties come in handy and a cordless drill. You've got to find a pathway through the firewall so a cordless drill and a step bit is going to be your best friend too. Now what have we got a coat hanger in the tool pile for? Well, we're going to show you and it's going to save you some time. But as with any wiring project step one is disconnecting the battery.

Keep in mind this kit comes with detailed instructions so all you have to do is follow along with them and you'll be fine. Now we're just going to expose the positive terminal since we're drawing power directly from here. With the door panel removed step one is locating the relays to the bolts that hold the armrest bracket on. Do this one at a time.

Now the long harness doesn't necessarily always go on the driver's side. Our battery is on the passenger side so the longer harness goes to the door that’s farthest away from your battery. This is the power feed from the cab and it goes in and loops around through here down to the motor so this is in fact a power source for a window lift motor. With your brown in your blue wire identified you want to separate them and get ready to make some connections. You want to expose your wires for your connections. Now the kit provides you with all the butt connectors that you're going to need to finish this project. However; we're going to do a permanent installation and solder the connections rather than use a mechanical connection. It's always more reliable to solder your electrical cables. First we'll connect the brown wire from the relay with the silver dashes to the brown wire that goes to the window switch. Cover up the connection with some shrink tube. Next we'll go from the blue wire with the white stripe from relay to the blue wire that goes to the window lift motor. Cover the connection shrink tube warm it up a little protect those wires Now keep in mind that with you door trim panel reinstalled there’s room underneath the bracket here for the relays and the wire so no worries on wire placement just yet. So now we're going to go with the brown wire with the blue stripe from the relay to the brown wire that goes to the window lift motor. If you find that your shrink tube doesn't really fit over top of the wires you're trying to fit it over here’s a trick. Use needle nose pliers and just gently spread the end of the shrink tube open to create more of an opening to slide your wiring in and usually works out pretty nice. There...The last connection is a blue wire from the relay gets connected to the blue wire from the window switch. I like to separate the strands twist them in opposite directions. That way you get the most current flow over top of this connection. Twist them together...ready for solder. Now the copper is going to change color just a little bit when it’s ready to take in the solder just like that it doesn't take much heat with a shrink tube just kind of an ideas you don't want to burn just want to shrink it around... there we go. I like wiring nice and neat so I'm just going to bundle these wires under here using plastic cable tie. You can get these at any hardware store, parts store, and home center just really nice to have around.

Next were going to pull the driver side kick panel off. Now this right here is the door harness and this is the seal. It's really tight so sometimes you need a little bit of persuasion. Be careful, you don't want to tear it. There you go and it just comes off and you’ve got access now to get inside there and get your wires. All right here's where the coat hanger comes in. It's got nothing to do with clothing. What you're going to do straighten out about maybe that much about a foot of it. With a pair of needle nose pliers you want to roll the end where it's smooth. That way it doesn't hang on anything what we're going to do is push it through the bellows between the cab and the door that way we can pull our wires back through we don't have to cut anything.

Taking our hanger out through here follow the harness through the bellows between the cab and the door and kind of just fish it through it it's a fiddly thing might take a little bit but you want to bend it into a u-shape and then just start working with it and that saves you from having to cut this bellows and feed your wire through there you never want to be destructive that way. Alright, so I got a coat hanger. Ok now we're going to do is connect our harness to the coat hanger and pull it through...Bob's your uncle... easy as pie. Now we can just feed the wiring through pulling the coat hanger while you're pushing your wiring harness. Okay, I can feel right there...there it is, love it, when a plan comes together. Then we just pull the wiring past the kick panel grommet and route the wiring to the battery.

Now, we'll button up our harness with some cable ties. Make it nice and neat. Now we're going to take the harness route it to the firewall tuck it under the carpet and go over to the other side because we're going through the firewall from the kick panel. Okay, now over here on the passenger side you can see where I've got my passenger door window harness wires running. Now this is the plug for the fire wall insulation pad we've sacrificed that and taking a step drill and just drilled out our whole so we've got plenty room for both wires without chafing the wires. So now it's just a matter of taking our two wires from the driver's door feeding them up in and they'll come out on the other side of the firewall and we'll fish them up through go straight to the battery. There it is there's our hot wire there's our ground. Just push'em through. Now we can make our connections. The inline fuse it's connected to our hot wire which happens, placing it up inside you can hear click. Okay, now it's firm.

Now while we're here we'll throw our fuse in, its's a 15 amp fuse. We can put this somewhere where we can find it and troubleshoot. LMC provides you plenty of wire to be able to tuck'em. We're going to strip the ends get ready for our connections, hot wire should give us plenty of room. Now, just like in the doors we're going to solder these to make a permanent connection. Okay, here's my ring terminal. What I'm going to do is feed it into where I've got a good solid connection there and give it a good crimp. All right we're going to do the same thing with the positive lead. Pull that guy loose, find a happy home- it's a happy little wire. Find a seat for the good crimp, here we go. Ba-Bam... Okay now we're going to solder our terminal ends but you never want to solder over top of your battery obvious reasons there’s fumes, don't blow yourself up. There we go... that's a nice solder joint right there.

Now if you forget to do your shrink tube like I just did. You could do a couple of wraps of electrical tape. It makes it look nice and neat and still protects the end of that joint. We’re going to take our fuse holders for the left and right sides just cable tie it neatly to the inside of the fender for their out of the way but we can find them if we have to change the fuses. Now connect driver and passenger hot to the battery we'll take a left and right grounds to the negative side.

Now we're ready for a test. That is awesome, that's exactly what we wanted to see. It's smooth in the up operation and smooth in the down operation. There’s no dead spot in the middle and that is precisely what the kit is designed to do. Drop power directly from the battery and just like a modern vehicle there's no slowdowns. Okay now, since this is a direct connection to the outside atmosphere use some RTV and seal it up. That way we're not going to have any moisture getting into the cabin. So with a couple of hours of your time and investing in the heavy-duty power window harness you can really improve the function of your electric windows in a 77 through 87 GM truck.

We hope we've passed on some common sense wiring skills to you as well. So keep in mind LMC Truck catalog there's tons of ways for you to get inspired on how to customize modernize or restore your truck. For now, I'm Kevin Tetz...we'll see you next time.

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