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- เผยแพร่เมื่อ 15 ก.ย. 2024
- This video discusses the problem and fix for the LMC Truck Heavy-Duty Power Window Harness, causing the 15A fuse to blow and the window not to operate. I was surprised when I started blowing fuses and I knew I had completed the wiring correctly. I assumed the new relay harness design and wiring was correct, just like anyone would. I wasn't looking for a problem, but found the solution. This is Part 1...see follow-up videos with additional parts for further on-truck demonstration.
I am SO THANKFUL you made this video. I have a 79 GMC that had the same problem! I appreciated this video more than you can imagine. I thought I was going crazy popping fuses because of the ground loop problem. Anyway, thank you so very much. May God overwhelm you and your family with blessings!
Had the same problem with my 78 GMC. You are the man! This had me scratching my head for a few days. I'm disappointed such a simple (not to denigrate your efforts!) is not prescribed in the (missing) instructions for this kit.
I managed to sort the problem out myself using a simple 5 pin switch. I worked only with the right/passenger door power lock, which is the one I need most to control when driving. I connected the switch straight to the positive battery terminal, with a wire going straight to the middle pin, then the next two neighbour pins were connected both to the chassis, and finally the two cables going to the door lock mechanism were connected to both ends -extreme ends- of the switch. By pressing the switch to one side the door locks, and by pressing it to the other side the door unlocks. There was no need to use relays. Pulling current straight from the battery is essential, otherwise the switch does not work. Thanks a lot.
I think it’s been stated already but my 87 C/R10 does not match your before diagram. My power window motor does not use body ground. There are 2 wires that complete the 12 volt circuit, up/down function is accomplished by reversing the power polarity of those 2 feed wires. So the relays connected the way the design is from LMC is correct for my installation. The 87A pin is used to facilitate ground in the “off” position. I am using my own relays not the LMC kit and your video really complicated things for me.
The difference I believe is that 77-81 models have a motor ground to the door frame and then just power either the up or down wire with the switch. These wouldn't need the 87a connection. But newer models, 82-87 have a different motor and the switch provides a ground one one side and power to the other, then reverses the polarity when the switch goes the opposite way. The motor on these doesn't have a separate ground so the 87a connection is a must for the later model motors to work. So for the older models, you would be of great benefit to simply put a ring terminal on at least one of the black wires you cut from 87a and attach it too your metal door frame. Otherwise you are still passing the ground side of the current through the old rusty hinges rather than your new ground wire in the kit.
Good information Jeff! I was pretty sure something like this was the case, since some folks seem to have no problem with the harnesses the way they come wired. I'm still not sure why LMC wouldn't just tell you this in the instructions so you can make the proper modifications to the universal harness kit for all these year models. Instead, we have to figure it out on our own by trial and error. Something I may not have made clear in my comments and video is I still ran the long black wires through the door bellows and the firewall, up to the battery. I then connected the other end closest to the relays with a ring connector to the mounting bolt/nut of the window regulator. Making a direct ground connection from the battery as close as possible to the window motor. There is just a short ground path through the motor mount on the regulator to the regulator mounting bolt/nut.
Great Video. Thank you for Sharing !
Thanks for posting this fix. It’s going to save much consternation for those of us trying to make the installation. I do have one question regarding the (LMC) instructions included with the kit. The BROWN and the BLUE wires were originally UP and DOWN from the window switch to the motor windings. It has to be a given that terminal 30 of one of the two new relays must be connected to the BROWN motor winding, and that terminal 30 of the other new relay must be connected to the BLUE motor winding (one for UP and the other for DOWN). The included instruction #5 directs us to connect relay BROWN/SILVER (probably terminal 86) to BROWN from the window switch, to energize the relay coil. So far - so good. Instruction #6 directs us to connect relay BLUE (from the same relay) to BLUE from the window switch. We now have both UP and DOWN from the window switch connected to the same relay - an error, in my opinion. Further, instruction #7 directs us to connect relay BLUE/WHITE stripe (probably terminal 30) to BLUE from the motor, powering one of the motor windings. No problem with that. But then instruction #8 directs us to connect relay BROWN/BLUE stripe to BROWN from the motor. We have now connected both UP and DOWN from the motor to the same relay - again an error, in my opinion. There is no further instruction for connecting the switch or the motor, and no mention of the second relay. Now I’m not an Electrical Engineer. I’m by both degree and profession a Mechanical Engineer, but I like to think that I do have a fairly decent grasp of motor controls and wiring logic. My question is this: what the heck? Am I missing something? I’ll be able to trace the pin functions, and probably wire the circuit correctly. But I thought I’d point out what I conclude as questionable (being kind) instructions. I’d like your take. Thanks Tony.
Sorry - color my face red!! I now realize that the wire colors coming out of the two relays are not the same. As a result the instructions make quite a bit more sense. 87 = red = +12v power to the motors; 87a = lg blk = gnd (cut = no connection); 86 = sm blk = coil gnd. These three are common to both relays. The two 85's and the two 30's are different. One relay has 85 = brown/silver and 30 = brown/blue. That relay connects the original brown wire circuit. The other relay has 85 = blue/silver and 30 = blue/white. Connect that relay into the original blue wire circuit. The only instruction that is not clear is instruction #6. Reads:...."connect blue wire from relay to blue wire from window switch". Should read:....."connect blue wire with silver dashes to blue wire from window switch". Otherwise pretty easy to connect circuits. Didn't mean to waste everyone's time.
@@paulparsons4950 Looks like you got it figured out. Hope everything went well for you.
@@tonycook8348 Hi Tony - Got my harness in and running fine. Thought I'd let you know a couple of issues I encountered. The first involves motor grounding. Without the black wire connection from terminal 87a, the only path for ground is via the window regulator mounting studs. There are several forum opinions out there which state that this path is (and always has been) inadequate. To help in grounding I ran a separate wire soldered into the battery ground lead to a terminal lug secured under the mounting stud nut (both doors). That takes painted door structure, hinges, etc. out of the loop. Seemed to help. Secondly, to help in fishing wires from the doors into the cab, I drilled fish holes directly opposite the door conduit. Much easier that trying to fish down through the grommet hole (too many bends to have to make). Then simply fish from there out the grommet holes. I also wasn't sure how to run the wires through the grommets and on to the battery. I couldn't find a source for new grommets, and therefor didn't want to ruin mine. My solution was to "drill" feed holes in the sides of my grommets. That also worked pretty well. I found out something interesting that I did not know. When testing the new relays on the bench, I discovered that primary side polarity didn't seem to make any difference. The relay closed the 87-30 circuit regardless of whether +12v was connected to 85 and ground to 86, or vice-versa. The only difference was +12v to 86 was a lot noisier. The primary side seemed to be gender-neutral. I connected mine per the instructions (and your diagram). Not sure if any of this helps, but thought I'd post it. Paul
@@paulparsons4950 hey quick question on your wiring. Ive been having trouble with this kit and it burning out the motors. Ima try your set up and see what happens but did you reground the 87a large black wire from the relays to a stud on the door and leave the same wire to the battery cut or leave the relay cut and ground the battery wire to stud? Thanks.
@@igivezerofox926 Hey Jonathan - Here's the series of events that led me to where I'm at: I first made the installation per the LMC instructions (without cutting the large black ground wire from the relays). Seemed to work okay, but like most everything I do, I wanted to see if I could hotrod-up the system and get the windows to run even "faster". I cut the large black wires per Tony's instructions. As a result my windows did not run at all. I could momentarily touch the ground wire and the windows worked; I could not touch the ground wire and the windows did not work. That's when I did some searching internet forums. I already knew that the only factory ground path for the motors was through the motor housings, back through the regulator mechanism, through the regulator mounting studs into the door structure, back through the door hinges and into the cab body to ground. The internet forums informed me that ground path was pretty much inadequate even when new from the factory. I decided that I probably should do something to improve that ground path. The LMC harness has a great ground return path already built-in with the ground wire running directly back to the battery. I could eliminate the painted door structure and the hinges. All I had to do was run a ground wire from the regulator mounting studs directly into the LMC harness ground wire. I had two choices how to do that (your question). Obviously I had to first fabricate a ground wire running from the regulator mounting stud using an appropriately sized lug. That part was easy. I then had to decide whether to run the newly fabricated ground wire directly to the cutoff battery ground wire, leaving the relay (87a) not connected, or to keep 87a connected and splice the newly fabricated ground wire into the ground return from 87a. This reply is getting pretty long but I’ve come this far, I might as well tell you the whole story. And this is the part about which you had asked. I don’t like compression/crimped connections when I can solder. I had already reconnected 87a previously to get my motors to run (and what a pain to re-solder and heat shrink those short leads). I felt like I had at most only one more chance to cut them again, and re-connect if I had to. So I decided to leave 87a connected for the moment and splice my new ground wire into the LMC ground. That’s a lot of fairly big wire to try to crimp (which I don’t like to do anyway), so I decided to solder and heat shrink. Naturally it was cold and windy that day, and there was no way my (even fairly hot) soldering iron was going to adequately heat the wires to solder, so I had to use a small torch. That worked great. I tried my windows and they ran hotrod fast. I stopped and declared success. Recap: I kept 87a connected, and spliced into the 87a ground return. Hope my long story not only tells you what I did, but why I did it that way. Paul
Tony, I use a chevy truck 86 model, k10, for a year already. The power window switches move up and down the windows satisfactorily, but the power door locks never worked. Today I decided to find out why, and saw that the 3 wires in both power locks were cut. The other end of these 3 wires has been covered with insulating tape. No current shows up in any of these wires. I do not know why someone in the past made the power locks inoperative by cutting these wires. There are 2 more cut wires inside each door leading to the door lock mechanism, also without current. The truck is in good condition and I would like to connect the power locks again and make them operational, but via relays in a way similar to the LMC design. Your videos and all the data shown here will be very helpful. Could you then, please, or someone else, tell me, in simple words, where from to draw current for the control side of the relays and how to give power to the lock switches? Thanks a lot in advance.
As far as the 4 videos you uploaded, you could have joined them before uploading them to TH-cam using the Quick Time Player, and then you could have converted the resulting mov file into a mp4 file via the Handbrake.
I didn't realize they made a kit. I just did all of this by hand. Without the ground loop, of course. 😂
Just been doing this week. It worked fine following the LMC instructions. Windows go up and down twice as fast. Still need to regrease components. Only issues I've had is that previous owner connected the wires to the connector to the driver side control using butt connectors and they've been coming apart so I am redoing with solder. Additionally, and maybe this is just my bad luck, the connector for the driver side came apart and all the wire connectors came out. I followed the truck's original wiring diagram to re-wire but it was confusing to interpret and that took a while.
That's great. What year, make, and model is this on?
I totally agree, there is no reason to ground the ckt on 87a. And yes that loop could be an issue if your schematic is correct (two windings with a common ground) would mean that you are pulling current through the opposite winding (the loop you pointed out).
Is it possible you have more resistance on your door gnd, and the path of least resistance was the loop? I would check that ground on the door since it seems most people are not having the fuse blowing issue. It may be that your motor ground on the door is a higher resistance, and current is being pulled on the opposite winding. Not to certain how the motor reacts to that, but If what I am theorizing is true, then the fuse would have blown almost at the instant you pressed the switch. If it blew after the switch was released , then I would be chasing and Inductive Spike, but I doubt that is what was happening.
Anyway by cutting out 87a to gnd., it resembles the original ckt, as the up/dn switch on the original makes no connection to a winding unless it's energizing a winding....Thanks for taking the time to show your efforts as that has helped me understand the potential problem that can occur with this kit. I am going to buy it, and do some tests, but again, nice work on the analysis.
Thanks, Biggie! I did some other testing that I didn't mention in my videos. I was also concerned about just using the ground connection from the window lift motor chassis, through the regulator mounting bolts, to the door sheet metal to make the ground circuit. I should mention at this point that I DID connect the original LMC long black ground wire directly from the battery neg terminal, ran it and the red pos through the firewall and through the door wiring harness bellows, to the area of the mounted relays. When I cut and removed the ground wire right from 87a, on both relays, I cut about a foot of the single blk grounding wire, leaving the 2 relay negatives connected together. I then added a ring connector to the cut end of this wire and ground off paint with my Dremel tool under one of the window track bolts and connected the relay grounds here. The other cut end of the blk grounding wire (from the battery neg) I also added a ring connector and connected it under one of the window regulator mounting bolts, after grinding off the paint. This is what I meant in the video when I said I had some additional wiring cleanup to do, including zip ties. This got me a direct connection from battery neg to as close to the window lift motor as possible, without having to run the wire inside the door and try to connect directly to the lift motor case. I was concerned about that wire possibly getting in the way of the window or the regulator mechanism and getting cut or broken (due to vibration). The additional testing I mentioned consisted of taking a heavy gauge jumper wire with alligator clips and connecting it from the grounding point on the regulator mounting bolt to one of the lift motor mounting bolts, effectively creating a lower resistance ground path as close to the motor case as possible. The bottom line was there was no noticeable difference in performance whether the ground path was through the wire or through the regulator itself. I knew that just relying on the ground connection path through the truck/door/chassis is not good, that's why I ran the original ground wire provided with the kit from the battery to as close to the lift motor as possible. I am relying on the short ground connection from the relay neg through the door sheet metal to the point where I connected the battery ground wire, at the regulator mounting bolt. I think everything should be fine. Glad the videos were of some help to you.
The point I used to connect the battery neg wire to the window regulator already had another ground wire from the window door wiring harness connected at this same point. I just added the battery neg ring terminal on top of this ring terminal, so both were stacked together at the same point.
@@tonycook8348 A wire from the battery negative is not necessary if the ground potential (metal on the door/window motor/mechanism) has a conduction path through the metal body components. A wire to negative battery could be considered a backup ground, but it serves the same function as the body metal, and could actually be more resistive as the metal structure potentially has a bigger diameter (more conduction) than the wire supplied in the kit. All of this would have to be measured to verify what I am theorizing an the grounding points throughout checked. There are instances where a path through the body metal can be problematic due to fastener oxidation or similar. In that case your wire could be the alternate route to prevent a bad ground. My approach to this is going to be 1- use your info and cut the 87a's out of the picture. 2-Run a single pos large wire (not sure what guage yet) from the Alternator to the Battery(for future alternator upgrade) ,3- then from that junction run another large wire to the junction on the firewall. 4-From the F/W junction I'll run the positives for the windows and for the ground I will run a wire from the door frame to the dash metal or check for existing wire and if I think it's suitable.
Thanks . Same problem.. I installed in driver side k5 blazer 1979 . And I try first without installing the passenger and blow up the fuse . So in just cut the black fat wires in all relays and that's all? Thanks
Tony, I presume that you will need to cut the 87a wires on both sides, i.e. Pass & drivers side kits. Correct?
Scott, you are correct, both sides (pass and driver) would need the 87a heavy gauge blk wire cut out on all 4 relays. But, I would caution cutting first before at least trying it the way the harness is wired already. Some have reported not having any problems with the original wiring. It's possible that other applications may use a different motor. If you try it before cutting, all you lose is a 15A fuse, if it blows. They sell the same fuses at Walmart for like $3 for a pack of 5.
Mine Worked flawlessly
Bill, if you don't mind me asking, what year model and make is the vehicle you did the installation on?
Hey Tony I know this a old thread but on my 90 suburban I installed lmc HD window harness but my driver window fuse has blown twice over the last 3 months (doesn't blow immediately)....passenger never had blown....any suggestions I ran across your video
I'm not for certain, but you might look at the window regulator and door window felt/rubber guides, or the window lift motor, as the problem. If the window regulator is not well lubricated (lithium grease), or the window door guides are old or dirty, the window will not move smoothly and draw more current when raising the window. Usually doesn't happen when lowering it. Also, the motor itself can cause a larger current draw if it is old.
@@tonycook8348 thanks for the suggestions Tony
what if i just get a 4 pin relay and wire it myself?
Starting burn fuse .. then I cut the two black fat wires came out relay now don't burn fuse but doesn't move the window . Is a click sound on the relays but no move the window.. ;(
Hi John. Sorry to hear you are having troubles. Have you verified that the window motor is OK? If you are hearing the relay "click" when you push the window switch up or down, sounds like you have the switch and relay connected correctly. Have you checked to be sure the window motor connector is connected and fully engaged? After that, have you checked to see if you get 12v (battery voltage) out of the relay on the larger gauge (fat) brown w/blue stripe and blue w/white stripe wires, which go to the window motor connector, when you engage the window switch (up or down), assuming the red relay wires are connected to battery voltage? If all these check out, I would start looking for a problem with the ground connections of the window motor case to the window regulator, the regulator to the door, and the door to the truck chassis. If you have run the black wire in the kit from the battery negative to the door or motor case, be sure there is nothing in the way of those connections, like paint or other insulators. I have some photos from my installation that may be helpful, if I had an email address to send them to. Hope this helps.
I wired mine without any issues? Works perfectly without altering how it was shipped..
That's fantastic! For some applications it works "as manufactured", without the modifications others need to make it work correctly.
Is there anyplace to get the "wiring directions" for this kit? I bought a truck that had a few new parts in a box....one was this kit. No paperwork or instructions. When I called LMC to get a copy, they basically told me I had to BUY the kit again to get them. ?! Didn't realize this was a state secret. There's dozens of drawings all over the i-net, was just wondering which one they used. Thanks for the vid Tony - TOP SHELF!
Jeff Z, thanks for your comment. I have scanned the 4 page installation instruction manual that came with my kit. I can send you the scanned images, but I need an email address. The only reason I can think of that they wouldn't/couldn't send you one is the instructions are included in the sealed bagged kit from their subcontactor and they don't actually have any of the manuals (still makes no sense). Let me know and I can get it to you.
@@tonycook8348 I sent you an email Tony - thanks very much!
Thank you for this. I am having the same problem on a G10 van I'm working on. But I am confused, while looking at the wiring to see if I screwed something up. It seems to me if you follow LMC directions, on the passenger side you would leave the brown and blue wires from the main drivers switch for the passenger door just using the original wiring of power through the drivers switch when using it. Am I supposed to cut and wire all 4 of the wires on the passenger side harness from the motor to the heavy blue and brown wires of the relay out ?
Hi Roger. I'm a little confused on exactly what you are asking. I don't want to tell you something wrong or confuse you more. You will cut the original heavy blue and brown wires in the harness on both doors in between the motor and the door window switch. The motor side of the original harness connects to the heavy blue/white stripe (to blue) and brown/blue stripe (to brown) of each pair of relays for both doors. The other end of the original harness from the door window switch connects to the smaller gauge blue/silver mark (to blue) and brown/silver mark (to brown). These are the coil wires on each relay. These wiring instructions are exactly the same as the instructions that come with the relay harness. I didn't change any of that. The only modifications come on the grounding side (black wires) of the relay harnesses.
@@tonycook8348 On my van the passenger motor has 4 wires going to it. 2 from the drivers door switch and 2 from the passenger switch. Even though the instructions don't mention the extra wires, I assume I need to attach all of the motor wires to the coil side with only the 2 heavy wires from the relays going to the motor, or I would be getting normal low voltage when operating the passenger window from the drivers side.
@@rogerzonnefeld6358 So, you're saying that the connector that plugs into the passenger side motor has 4 wires; 2-blue and 2-brown? What year model is your van? I am not an expert on all the differences of the various year models and specific wiring applications. On my 80 Blazer the wires from the driver side switch to the passenger side motor connects into the original wiring harness on the passenger side AFTER the passenger side switch, but there are still only 2 wires going directly to the motor connector. If yours actually has 4 wires (2-blue, 2-brown) at the connector on the passenger side, I think you are on the right track. Are the 4 wires connected to a 2-lug plug (blues together and browns together), or does each wire have its own separate position in the plug (4-lugs)? If 2-lugs, this should work. Cut the 4 wires going to the motor connector, you would connect the 2 blue wires from the motor connector to the blue/white stripe heavy wire on the relay, and the 2 brown wires to the brown/blue stripe on the other relay. Connect the switch ends of the 2 blue wires to the blue/silver mark coil wire on one relay, and the 2 brown wires to the brown/silver mark coil wire on the other relay. If this sounds correct, it should work. I make no guarantee. If there are 4 separate wires in the motor connector, I have no idea how these wires are used inside the motor. If they are simply connect to each other (blue to blue and brown to brown) inside the motor, then you should be able to do the same thing already described above. Good luck!!!
@@tonycook8348 The van is a 1979. Yes the motor has 2 blue and 2 brown tied together at the the 2 pins going into the motor. 2 from the passenger switch and 2 from the drivers switch. So first I'll remedy that and tie them all together to the coil side and see if that fixes the fuse situation. And then try your ground fix to see if that is my problem. Thanks for your help
@@rogerzonnefeld6358 BE CAREFUL. I'm not sure what you mean when you say "tie them all together to the coil side". They should still be kept separated and grouped by color codes, as I mentioned in my previous post. You will never be connecting more than 3 wires together at one time (2 original to 1 new from the relay harness). The coil wires control the up/down function now instead of the switches. The switches control the coils. The relay provides the 12v to the window motor, depending on which relay is activated (up or down). You need to be sure you have this wiring done correctly BEFORE you try to determine what needs to be done on the ground side of things...maybe nothing.
So do you cut both big black wires on relays?
Yes. There are 2 bigger black wires on BOTH of the two different window harnesses. Each harness has 4 black wires (2 larger, 2 smaller) connected together under a heat shrink tube. Cut the 2 larger gauge black wires. Leave some room to reconnect if this does not work for your particular application. Once functioning is confirmed you can trim the relay side wires all the way to the bottom of the relay socket. Do the same for the other harness. Check one harness opetation first before doing both.
Could I give you a call and ask u what wires I need to cut and splice
Josh, are you experiencing fuses blowing using the kit, or are you trying to do this modification ahead of installing on your vehicle? What is your application (make, model, year)? I have some additional detailed photos from my installation that I think would help. I don't know that there is a way to use TH-cam to send these to you, or a way to do this in private without everyone else seeing personal contact info. I would be willing to send my pics if I had an email address to send them. This could be a start.
Could this also burn out the window motors? Ive gone through 3 already after I installed this kit
I don't know that I have enough information to answer this. What is your application (make, model, year)?
@@tonycook8348 its an 84 Chevy c10
Just curious, where were your motors manufactured...China? In other TH-cam videos I watched, I heard comments about problems with China manufactured motors burning out after just a few years of use. Sounds like yours went out very quickly. Have you taken a meter to check if the two motor leads are connected to the case? I do not have any experience with this style of motor. I assume that the wiring connector to the window motor only has 2 wires...1 for up, 1 for down and no additional ground connection?
@@tonycook8348 Ya I honestly would think its just due to cheap china parts. They are made in china, dorman motors from Oriellys. Both leads are good and yes its just two wires leading to the motor. Im gonna try Paul's layout for grounding and see if anything changes.