All right today we are going to go over how to check over a modulite as shown right here which converts a 5 wire to a 4 wire system. We are going to go over the basics which are really simple. Basically we are just going to test input into the modulite and test the output of the modulite. That will tell us one of two things, we have no input going into the modulite, that means there is something wrong on the car side of the connector, there is nothing wrong with the modulite. If you have power going into it, but nothing coming out then you know chances are it is the modulite or there is a problem on the trailer itself. When testing you always want to test these modulites or converter boxes without the trailer hooked up first.
So you rule out either A the trailer, B the converter box, or C the car it is hooked up to. Get yourself a good light tester, one that has an incandescent light that will withdraw enough power to give it enough load for the converter to work against. And of course this is your ground connection. All right and starting off what you want to do is take what you used for your ground wire on your wire harness you want to stick your ground clip of the tester to the same place. That will tell us if you have power going into it and will also tell us if the ground you are using is good also. We will go ahead and ground this to the same ground that we used for our wire harness here.
And so at this point we will go ahead test power. The first thing we are going to test is the black wire right here. And what that is going to do is make sure we have power going to be connected directly to the battery. So first off you want to make sure you have a good fuse going up to the battery. Check that, when that is good go ahead and make sure your have power going into the box. That way you know if you have any power interruptions or a bad connection or something like that. You are going to take your light tester and pierce the wire, and check for power. And we have power right here, so we know we have power going into it. And for the rest of the wires you probably want make sure you keep the engine on or at least the key on the on position so all the electronics are working in the vehicle. So then you will simply go through the rest of the wires and check to make sure you have power going into the box. So we will do the stop light circuit first which is going to be the red wire. Okay with the brake pedal pushed down the red wire lit up so we have power going in there, so that is good. Now the same thing, we will turn on the right-turn signal. So we have a right turn going in. So we will do the same thing for the left side. So now we know we have power going through the yellow, so that connection is good. The next thing will be our running light circuit, which is the brown wire. Okay so we have power going in there. So we have all the power going into it.
If you did not have power going into it the problem is one of two things, one it is either the physical connection to the car itself or two the ground is not good enough to begin with. So what you want to do is go ahead and find a different place to ground the wire harness at. Hopefully there is a piece of sheet metal or maybe you can find a factory wiring ground somewhere beneath the carpet somewhere in the vehicle. Or if you are not sure where to ground it one other option is to run a temporary ground from the white wire up to the negative post of the battery. That way you know you have a good ground and you can test your wires that way. That is another way you can check your input, so that is how you test your ground. So you have that car side covered, now what we are going to do is check the output to the trailer.
Again it is the same thing as before. So we left off with the running lights so we will go ahead back to the running light circuit on the brown wire on output. So that is good. Now do the same thing on the right-turn signal. What you want to do is test both sides of this because what happens inside the modulite is that it combines the brake signal coming from the red with green and yellow. So it brings it down to a four wire system. Now I have a good right-turn signal so I will do the same thing with the left-turn signal. We are good there too. Okay, you do not have to worry about the ground wire on this side because we already verified the ground on the input side. So if you have everything working as shown here that means this converter is working as it is supposed to. So the problem is probably going to be further down the road. It can be A, a dirty connection going to the trailer or B, it can be a problem within the trailer itself somewhere in the wire harness or tail light.
Questions and Comments about this Video
driver side blinker light stays on passenger side is fine can you help me please
comment by: kyle l - 10/13/2012
The best thing you can do to start narrowing down the problem is check the wires right at the box. Use a circuit tester with a sharp probe and test the wires going into the box. If everything operates as it should going in, then check the wires coming out. If not all signals are properly going in, then check your connections to the vehicle. If you check the wires in and out, and both sides are fine, then you may have a ground issue with the trailer. Make sure the ground wire on the trailer side harness is securely connected to the trailer frame and the connection is free of corrosion. If the wire signals go in the box fine, but are not coming out as they should, then the box may need to be replaced.
Patrick B - 10/15/2012
Today on our 2005 Chevy Silverado, we are going to hook up the hot lead for the seven pull connecter at the back of the truck. To do this well simply remove the fuse box cover and the first position, on the first row is a blank fuse, we are going to remove it and install a 30 amp fuse. With that fuse installed, we can go ahead and replace the cover and were now hot at our seven pull connector. There you have it with the install of the hot lead fuse on our 2005 Chevy Silverado.
How To Troubleshoot a Modulite Demo
Today we are going to troubleshoot a modulite that is not really working so we will check it out and show you what to look for. This will apply to all modulites and this will also apply to converter boxes as well. The only difference being that it does not have a power wire for a converter box. The first thing we want to do is put a tester on the 4-pole just to make sure. We will hook up our ground to our ground lead and then we will turn on the left turn signal which we have going, we have got nothing. You can turn on the other signals and see what we have got, nothing here. Try the running light circuit, nothing here either. 00:28
How To Differentiate a Two Wire and Three Wire System
Today we are going to do the Frequently Asked Questions of what is the difference between a three wire system and a two wire system. It is actually very easy and very simple. All it is, is you take away two wires and the same thing applies to the four and five wire system. Starting off on the car side we are going to attach the wiring to, we are going to have five wires. Green is going to be right turn, red is going to be the brake signal, yellow is going to be left turn, brown is going to be your running lights, and the white is going to be ground. When you talk about the three wire system you are only talking about the right turn, the brake signal, and the left turn. You omit the brown wire and the white wire. That is our three. On the two wire system you are only dealing with the two combined signals, the brake signal and the turn signal on the same wire. We are only dealing with the left and right turn. 00:46
Trailer Wiring Harnesses Troubleshooting
Today we are going to cover kind of a different subject. Basically, we are going to talk about getting your wiring installed and what is happening afterward. Okay, for instance, you went to the trouble to get your wiring installed, you plug it into your trailer, and nothing happens. There could be a lot of different things going on with it. First off, you need to figure out for sure whether it is on the towing vehicle side - the car or truck - or if it is something on the trailer. We will show you how to test the different types of wiring systems we have shown here. And that way you can tell for sure if it is your wiring harness or if it is your trailer.
T-One Wiring Harness Explanation
Today we are going to show you a little bit of wiring. Basically kind of like wiring 101 and what to look for when your going to hardwire into the vehicle. What hardwire means is actually getting to the wire and splicing into them to make a connection. T1 connectors are different. They actually have a connection point and harness which you take apart and fit the T in the middle of that. Now on this vehicle we will show you the typical wiring schematics and a couple variants from that. The typical connection point is like where this wiring comes into the back of the tail light and there is always going to be a connection point, almost always. Older vehicles, it would have just ran straight, but with pretty much of your newer vehicles you are always going to have a snap connection like this. Basically a T1 connector simply would just go ahead and fit in between this harness.
