Problem in wiring on truck, for trailer connection.
- Thread starter Selahdoor
- Start date
Jesus Freak
Full Access Member
Don't you just love chasing electricity! Thankfully it's not a Dodge, nothing but electrical problems in my experience. And what's really fun is it's all "electrical theory" so in "theory" Salahdoor's problem could be completely unique to his situation and never rear it's head to anyone else.......in theory. But I feel for you Sir, chasing a wire and the rain won't stop, dang! Happy Independence Day! Read the Declaration of Independence, the fireworks are in the document!
Have you checked the bulb? It's two elements in one bulb (1157)
What about the socket? They can get cruddy on one of the contracts but not the other. Just trying to cover the basics.
Works fine on other vehicles.
i though it was the light on the truck not working
I explained it thoroughly.
Everything works fine on the truck.
It just doesn't get communicated to the trailer correctly.
Trailer works perfectly on other vehicles.
Ergo, problem is in the wiring for the trailer connection.
Everything works fine on the truck.
It just doesn't get communicated to the trailer correctly.
Trailer works perfectly on other vehicles.
Ergo, problem is in the wiring for the trailer connection.
My fault, sorry. I totally misunderstood.
Probably.
The issue is the _interface_ between the truck and trailer, which does not limit it to the trailer wiring on the truck.
Suppose the other trucks have a solid ground through the hitch and this one doesn't so the trailer ground wire problem only shows up on this truck
Or maybe the other trucks have combined brake/turn lamp and this truck has amber turn signals requiring "conversion" for a trailer with combined brake/turn? (I don't know the IDI trucks very well...)
Due to ohms law, I have learned to not trust the results from a meter only. Poor connections can measure fine but fail oddly under load so a test light (not LED) or the trailer lights are a better test. I have a "breakout" cable for my tow vehicle connector that makes it easy to re-assign pins so I can - say - swap L and R, or use "tail" to light up turn signals to help with troubleshooting.
Another useful test is to NOT have the trailer hitched so the hitch ground is removed from the possible muddling of results.
Very good!!! Thank you. You definitely have a good understanding.
With this particular trailer, there HAD been a problem with the ground. The trailer was not working correctly, on any vehicle.
I worked on the trailer wiring first. I figured out that the ground was indeed bad on the trailer. I replaced that. Cleaned the surfaces. Put a new connection on with a stainless bolt, and plenty of dielectric grease, and now the trailer works perfectly on any vehicle.
And yes, I did this with the cable connected to the owner's truck, but NOT hitched up, precisely because I didn't want a false ground situation.
Further, I figured out that the trailer's owner hadn't realized the problem for years, because indeed, he had gotten a good enough ground connection between the trailer and the truck, through the hitch. It had just finally gotten bad enough that that didn't work any more. (I think that enough old grease has hardened and built up, in the hitch, that it insulates between the ball and hitch. And the chain connection is rusty enough that even that would no longer provide a good enough ground.)
As I said, once the ground was perfected, the trailer now works perfectly on any other vehicle. It is only mine that has this problem.
So, today, I will be troubleshooting that interface.
I was about to head out the door to go use an analog test light on the connections in the adapter. Decided to stop and check if there were any responses to this thread before heading out.
I will also test with a meter for continuity for things like the ground.
I will be doing the testing and writing down the results. I will report back in here with the results. Then I will go out and crawl under and start inspecting wiring. Starting with the ground for the truck adapter.
Although I have to say, given the experience, the ground at the adapter is not high on my list of suspects.
Given that the trailer did not work on any vehicle... equally. Including mine. It malfunctioned exactly the same way on every vehicle.
Then once the ground on the trailer was fixed, the trailer started working on every vehicle. Including mine. Except that mine still has that problem with the right taillight connection.
The ground problem was fixed via the white wire that comes from the truck. Now the ground is fully functional through that wire from truck to trailer. And since it is working through my own connector as well, I find it unlikely any more, that the problem on my truck is with the ground.
I am thinking I am going to find a problem in the wiring that goes between the truck wiring, and the connector right turn signal wiring.
We'll see.
With this particular trailer, there HAD been a problem with the ground. The trailer was not working correctly, on any vehicle.
I worked on the trailer wiring first. I figured out that the ground was indeed bad on the trailer. I replaced that. Cleaned the surfaces. Put a new connection on with a stainless bolt, and plenty of dielectric grease, and now the trailer works perfectly on any vehicle.
And yes, I did this with the cable connected to the owner's truck, but NOT hitched up, precisely because I didn't want a false ground situation.
Further, I figured out that the trailer's owner hadn't realized the problem for years, because indeed, he had gotten a good enough ground connection between the trailer and the truck, through the hitch. It had just finally gotten bad enough that that didn't work any more. (I think that enough old grease has hardened and built up, in the hitch, that it insulates between the ball and hitch. And the chain connection is rusty enough that even that would no longer provide a good enough ground.)
As I said, once the ground was perfected, the trailer now works perfectly on any other vehicle. It is only mine that has this problem.
So, today, I will be troubleshooting that interface.
I was about to head out the door to go use an analog test light on the connections in the adapter. Decided to stop and check if there were any responses to this thread before heading out.
I will also test with a meter for continuity for things like the ground.
I will be doing the testing and writing down the results. I will report back in here with the results. Then I will go out and crawl under and start inspecting wiring. Starting with the ground for the truck adapter.
Although I have to say, given the experience, the ground at the adapter is not high on my list of suspects.
Given that the trailer did not work on any vehicle... equally. Including mine. It malfunctioned exactly the same way on every vehicle.
Then once the ground on the trailer was fixed, the trailer started working on every vehicle. Including mine. Except that mine still has that problem with the right taillight connection.
The ground problem was fixed via the white wire that comes from the truck. Now the ground is fully functional through that wire from truck to trailer. And since it is working through my own connector as well, I find it unlikely any more, that the problem on my truck is with the ground.
I am thinking I am going to find a problem in the wiring that goes between the truck wiring, and the connector right turn signal wiring.
We'll see.
Ok, here is the testing results. Pretty much what I expected.
Before I start I will say that it looks like I may be right and wrong at the same time. I think the problem is SOMEHOW a ground problem, but only on the right turn signal/stop connection. And only on the connector, and not on the truck's lighting.
Here is the connector. I have numbered each contact. Even on the built in 4-flat connector.
1 is running lights.
2 is left turn signal and stop.
3 is ground.
4 is electric brakes.
5 is right turn and stop.
6 is constant power.
7 is right turn and stop.
8 is left turn and stop.
9 is running lights.
10 is ground.
The results...
Continuity tests with the truck turned off, all lights off, etc...
C between known ground, (Bumper.), and #s 2, 3, 8, and 10
C between any combination of the above numbers.
NO continuity between 5 and anything else.
Test with analog test light.
With the truck turned off, and no running lights on...
With brakes on... #s 2 and 8 light up. Not # 5
Brakes off, hazard on. 2 and 8
Left turn, 2 and 8
Right turn, nothing
Running lights, 1 and 9
Key on, nothing else, # 6. (#6 does not light up unless key is on. So that 'constant power" is only when the key is on.)
Every light on the truck itself works exactly as it should. Absolutely no problems there.
This testing cuts out the trailer. But remember that on the trailer, any time that right turn, or stop light is activated, the complete light on the right side, turns off. No dimming no brightening, no blinking. It just turns off.
Ok, so what this tells me, so far...
It would be logical, without that last bit of info, to assume that there simply isn't any signal from the connector to the trailer, for the right turn signal/stop contact.
Nothing at all seems to be happening with that contact. No ground. No continuity. No light. Just zero response for anything at all on that #5 contact.
But if you add the last bit of info, then it is obvious that SOMETHING is happening through/with that contact, because the running lights come on, on the trailer just fine, but that right light gets interrupted when the right turn, or brakes, or hazard are turned on.
So, the problem is isolated to the wiring going to the right turn/stop contact in the connector.
Maybe it's a ground problem. Maybe the wire is grounded out somehow. I don't know.
A grounded out situation seems precluded by the fact that it doesn't present as a ground in the testing. If it were shorted to ground somehow, then it should ALWAYS present as a ground, in the testing.
Instead, my gut is telling me that it is the lack of ground that is the problem. When that circuit is activated, there is no ground for it to go to. and it gets fed back through the wiring, instead. Which actually turns off the light.
But that doesn't seem to make sense either. It seems to me that the lights themselves are providing a ground.
If some sort of positive signal made it through, the light should operate.
But how is it that opening that circuit results in that light essentially getting all ground, and no power? When neither ground nor power are available from that contact?
Frankiln's explanation makes the most sense here. Even so, I have yet to be able to wrap my thinkerer around how that happens. Or what the solution might be.
I AM sure that the problem is between the contact that you can see in the pic, (#5), and the wiring on the truck. I really don't think it's the truck wiring. Or the trailer wiring. It's what runs between the truck wiring, and that contact...
Is it broken?
Is it grounded out?
Is it wired up to the wrong thing?
Those are the questions I am going to be answering for myself, when I go out there and crawl under the truck to have a look at the actual wiring...
Here's another twist in the plot.
The only extra wiring that I know of in the circuit, is a third brake light that I wired in, myself.
To do that, I ran an independent 10ga wire all the way back from the battery. And I ran a new ground wire, just for this. So neither of those are anywhere near the trailer wiring. They go to the relay I installed, that actually powers the 3rd light.
But... I had to have a signal from the brake light. So, I had to tie into the truck wiring for that signal.
The 3rd brake light only comes on with the brakes. It doesn't operate when either turn signal, or the hazard lights operate. So I don't think I somehow got tied into the right turn signal wiring.
But I guess we'll see...
Maybe I should disconnect that relay, and see what happens with this contact... First thing I'll do, right now.
Before I start I will say that it looks like I may be right and wrong at the same time. I think the problem is SOMEHOW a ground problem, but only on the right turn signal/stop connection. And only on the connector, and not on the truck's lighting.
Here is the connector. I have numbered each contact. Even on the built in 4-flat connector.
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1 is running lights.
2 is left turn signal and stop.
3 is ground.
4 is electric brakes.
5 is right turn and stop.
6 is constant power.
7 is right turn and stop.
8 is left turn and stop.
9 is running lights.
10 is ground.
The results...
Continuity tests with the truck turned off, all lights off, etc...
C between known ground, (Bumper.), and #s 2, 3, 8, and 10
C between any combination of the above numbers.
NO continuity between 5 and anything else.
Test with analog test light.
With the truck turned off, and no running lights on...
With brakes on... #s 2 and 8 light up. Not # 5
Brakes off, hazard on. 2 and 8
Left turn, 2 and 8
Right turn, nothing
Running lights, 1 and 9
Key on, nothing else, # 6. (#6 does not light up unless key is on. So that 'constant power" is only when the key is on.)
Every light on the truck itself works exactly as it should. Absolutely no problems there.
This testing cuts out the trailer. But remember that on the trailer, any time that right turn, or stop light is activated, the complete light on the right side, turns off. No dimming no brightening, no blinking. It just turns off.
Ok, so what this tells me, so far...
It would be logical, without that last bit of info, to assume that there simply isn't any signal from the connector to the trailer, for the right turn signal/stop contact.
Nothing at all seems to be happening with that contact. No ground. No continuity. No light. Just zero response for anything at all on that #5 contact.
But if you add the last bit of info, then it is obvious that SOMETHING is happening through/with that contact, because the running lights come on, on the trailer just fine, but that right light gets interrupted when the right turn, or brakes, or hazard are turned on.
So, the problem is isolated to the wiring going to the right turn/stop contact in the connector.
Maybe it's a ground problem. Maybe the wire is grounded out somehow. I don't know.
A grounded out situation seems precluded by the fact that it doesn't present as a ground in the testing. If it were shorted to ground somehow, then it should ALWAYS present as a ground, in the testing.
Instead, my gut is telling me that it is the lack of ground that is the problem. When that circuit is activated, there is no ground for it to go to. and it gets fed back through the wiring, instead. Which actually turns off the light.
But that doesn't seem to make sense either. It seems to me that the lights themselves are providing a ground.
If some sort of positive signal made it through, the light should operate.
But how is it that opening that circuit results in that light essentially getting all ground, and no power? When neither ground nor power are available from that contact?
Frankiln's explanation makes the most sense here. Even so, I have yet to be able to wrap my thinkerer around how that happens. Or what the solution might be.
I AM sure that the problem is between the contact that you can see in the pic, (#5), and the wiring on the truck. I really don't think it's the truck wiring. Or the trailer wiring. It's what runs between the truck wiring, and that contact...
Is it broken?
Is it grounded out?
Is it wired up to the wrong thing?
Those are the questions I am going to be answering for myself, when I go out there and crawl under the truck to have a look at the actual wiring...
Here's another twist in the plot.
The only extra wiring that I know of in the circuit, is a third brake light that I wired in, myself.
To do that, I ran an independent 10ga wire all the way back from the battery. And I ran a new ground wire, just for this. So neither of those are anywhere near the trailer wiring. They go to the relay I installed, that actually powers the 3rd light.
But... I had to have a signal from the brake light. So, I had to tie into the truck wiring for that signal.
The 3rd brake light only comes on with the brakes. It doesn't operate when either turn signal, or the hazard lights operate. So I don't think I somehow got tied into the right turn signal wiring.
But I guess we'll see...
Maybe I should disconnect that relay, and see what happens with this contact... First thing I'll do, right now.
I'll reiterate... In @franklin2 's explanation, if the ground on the light itself is bad, the voltages meet, and cancel each other out. The light goes out.
But the light on the trailer is fine. It works perfectly on all other vehicles.
It only does this, when connected to my vehicle. And I have already explained how the circuit for #5 contact seems to be just plain non-existant, for power or ground either one, in the testing...
But the light on the trailer is fine. It works perfectly on all other vehicles.
It only does this, when connected to my vehicle. And I have already explained how the circuit for #5 contact seems to be just plain non-existant, for power or ground either one, in the testing...
Thinking about all this, I did another continuity test.
Is there continuity between ground and #'s 2 and 5, while brakes or turn signals are on?
While nothing is on, 2 grounds.
While brakes, hazard, or left turn signal are on, #2 loses ground.
There is never a ground on #5, no matter what.
Is there continuity between ground and #'s 2 and 5, while brakes or turn signals are on?
While nothing is on, 2 grounds.
While brakes, hazard, or left turn signal are on, #2 loses ground.
There is never a ground on #5, no matter what.
Jesus Freak
Full Access Member
I'd hire Columbo. He'd figure out who killed the ground.
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