Problem in wiring on truck, for trailer connection.
- Thread starter Selahdoor
- Start date
You missed the center contact on the 7-pole round.
Continuity is a handy tool for quick checking. But it can report "connected" when there is not a good enough connection to keep a brake light on as well as showing continuity _through_ the brake/turn light as you are reporting.
What about 5 to 7. Those _should_ be connected together...
I want to be sure I understand. If the tail lights are on, the right trailer lights up. Activate right turn and the trailer right tail light turns off:
*1 - the entire time the right signal is activated, or
*2 - anytime the right turn signal is supposed to be glowing
#2 would mean the trailer right tail blinks, but opposite of the turn signal.
If it's #1, then it is not a simple wiring/ground problem.
Sometimes is better to think of the system with ground being it's own wire rather than chassis. But this is a puzzler either way.
All power and no ground (return) will produce the same symptoms.
I came up with a wiring that would produce your symptoms. But I don't know how it could exist with the truck and trailer connector. It involves the "return" for the right turn/tail lamp being connected to #5 and the "hot" for the right turn/tail lamp being disconnected.
Again, I don't know how this could exist in the trailer connector on the truck. If the truck has a ground wire for the brake/tail lights and not just chassis, maybe.
Or if the truck has amber turn signals and so needs to be converted to combined turn/brake for the trailer.
I would expect that to effect both left and right..
Some things that might help - or confuse things further...
Take out the tail/turn lamp (light bulb) from the truck. Does that change how it measures or behaves? I agree that it seems unlikely the truck wiring _to_ the light is a problem.
check for continuity between #5 and #7 (7-pin right and 4-pin right). Use a test light on the 4-pin terminals while the trailer is connected to see what is lighting up.
Try jumping left and right on the 4 pin (7-8) and see if the trailer right turns on with the left.
Since I don't know how the truck right light assembly is wired to the trailer connector, I would be suspicious of the right truck light. Yes, even though on the truck it is working.
Ok, I got it fixed, but I'll answer a question or two. Then explain what happened after...
This is in reference to my third brake light, and I agree:
Ok, I'll show the problem and solution in the next post. But first I want to say something.
Yall are all free to laugh at me now. I don't mind.
The solution was very simple. The problem was very easy to locate. It took maybe 5 minutes of being under the truck, to find the problem, and another 15 or so to figure out the solution, and make the fix.
I could have just done that in the first place. Yes it seems like I wasted a bunch of time. But if I had it to do all over again, I would do it the very same way.
The reason why is....... Just as you have to exercise your muscles or they will atrophy... The same goes for your brain.
I am 65 years old. Many people my age are 'losing it', because they simply stop exercising their brains. I don't want to be one of those. So, I look for challenges of this sort, to try to work out, in my brain, before I actually lay my hands on anything.
Most of you are a fraction of my age. And as I said, you are free to laugh. I will laugh right along with you. But while I do, I'm also going to be flexing my brawny brain at yall!
That is for reverse lights. Not used on the trailer. Not even connected to anything on the truck contact.
I was using continuity ONLY for a secondary 'feedback' as it were. Relying mostly on the analog light.
It's too late to make these tests. But I wish I had. It would have added to the clues the fun and the challenge.
Yup.
This is in reference to my third brake light, and I agree:
Ok, I'll show the problem and solution in the next post. But first I want to say something.
Yall are all free to laugh at me now. I don't mind.
The solution was very simple. The problem was very easy to locate. It took maybe 5 minutes of being under the truck, to find the problem, and another 15 or so to figure out the solution, and make the fix.
I could have just done that in the first place. Yes it seems like I wasted a bunch of time. But if I had it to do all over again, I would do it the very same way.
The reason why is....... Just as you have to exercise your muscles or they will atrophy... The same goes for your brain.
I am 65 years old. Many people my age are 'losing it', because they simply stop exercising their brains. I don't want to be one of those. So, I look for challenges of this sort, to try to work out, in my brain, before I actually lay my hands on anything.
Most of you are a fraction of my age. And as I said, you are free to laugh. I will laugh right along with you. But while I do, I'm also going to be flexing my brawny brain at yall!
The problem was pinpointed when I said it seems like there is no ground, OR power coming from the #5 contact.
It was like it just wasn't even connected.
Well, that was the case. The wire from that contact, had been pulled loose from wherever it had been connected before. It was just hanging loose there, with the end stripped, and looking like it had been twisted to another wire, then pulled loose.
Problem was, there was no wire under there that it could have been pulled loose FROM. Nowhere!
So I spent about 15 minutes moving wires and connectors around, crawling my creaky old bones under the truck, back out, back under, etc, switching lights, brakes, waiting for the test light to light up...
And FINALLY found the wire that feeds the signal to the right brake light.
Lengthened the wire that comes out of the back of the contact, and spliced it into the turn signal feed wire.
Problem fixed.
Reconnected to the trailer, and the trailer now works perfectly as well.
~~~~~~~
But now I hope someone with a bit more knowledge about this stuff, can explain to me how not having contact #5 connected to anything at all on the truck.... (It was just a dead end on the connector.)
Leads to the light on the trailer working fine on the running lights, but getting turned completely off, when the right turn signal or brake are activated on the truck.
No signal of any kind was getting from the truck to the trailer through that contact. It wasn't sending power to the light. And it wasn't acting as a ground for the light. So how could it possibly have had any affect at all on the light on the trailer?
It was like it just wasn't even connected.
Well, that was the case. The wire from that contact, had been pulled loose from wherever it had been connected before. It was just hanging loose there, with the end stripped, and looking like it had been twisted to another wire, then pulled loose.
Problem was, there was no wire under there that it could have been pulled loose FROM. Nowhere!
So I spent about 15 minutes moving wires and connectors around, crawling my creaky old bones under the truck, back out, back under, etc, switching lights, brakes, waiting for the test light to light up...
And FINALLY found the wire that feeds the signal to the right brake light.
Lengthened the wire that comes out of the back of the contact, and spliced it into the turn signal feed wire.
Problem fixed.
Reconnected to the trailer, and the trailer now works perfectly as well.
~~~~~~~
But now I hope someone with a bit more knowledge about this stuff, can explain to me how not having contact #5 connected to anything at all on the truck.... (It was just a dead end on the connector.)
Leads to the light on the trailer working fine on the running lights, but getting turned completely off, when the right turn signal or brake are activated on the truck.
No signal of any kind was getting from the truck to the trailer through that contact. It wasn't sending power to the light. And it wasn't acting as a ground for the light. So how could it possibly have had any affect at all on the light on the trailer?
Last edited:
Jesus Freak
Full Access Member
Right on Salahdoor!!! I'm 41 this year, and most of the people my age stare at me like I'm an idiot because my newest vehicle is a 1990 and I buy broke stuff make it work and sell it to them! For profit!!! Nothing like going Columbo on a mechanical or electrical problem. Keep on truckin' BRO! I've really digged reading this mystery novel of a thread, can't wait to hear who killed the guy. He deserved it, though. I mean acting like a Dodge with weird electrical problems!Ok, I got it fixed, but I'll answer a question or two. Then explain what happened after...
That is for reverse lights. Not used on the trailer. Not even connected to anything on the truck contact.
I was using continuity ONLY for a secondary 'feedback' as it were. Relying mostly on the analog light.
It's too late to make these tests. But I wish I had. It would have added to the clues the fun and the challenge.
Yup.
This is in reference to my third brake light, and I agree:
Ok, I'll show the problem and solution in the next post. But first I want to say something.
Yall are all free to laugh at me now. I don't mind.
The solution was very simple. The problem was very easy to locate. It took maybe 5 minutes of being under the truck, to find the problem, and another 15 or so to figure out the solution, and make the fix.
I could have just done that in the first place. Yes it seems like I wasted a bunch of time. But if I had it to do all over again, I would do it the very same way.
The reason why is....... Just as you have to exercise your muscles or they will atrophy... The same goes for your brain.
I am 65 years old. Many people my age are 'losing it', because they simply stop exercising their brains. I don't want to be one of those. So, I look for challenges of this sort, to try to work out, in my brain, before I actually lay my hands on anything.
Most of you are a fraction of my age. And as I said, you are free to laugh. I will laugh right along with you. But while I do, I'm also going to be flexing my brawny brain at yall!
Well done!
I tried to draw a schematic of a circuit that would duplicate your symptoms with the info I have. If the ONLY problem was the wire from truck right turn was not connected to trailer connector #5, I can not figure out any possible way.
The way a lamp will turn _off_ when feeding power is if the other side of the filament already has power. Staring at this schematic... I'm still suspicious of a "return" and "hot" mis-wire. It will cause the symptoms you experienced, but not sure how to actually set up the truck and trailer that way!
What color was the wire attached to the trailer connector? And/or the color you eventually connected _to_? Not worth going back under just to check - but if you remember maybe it will shed some light.
Honestly, I think it is impossible. Unless... there is something else not quite right with the wiring.
I tried to draw a schematic of a circuit that would duplicate your symptoms with the info I have. If the ONLY problem was the wire from truck right turn was not connected to trailer connector #5, I can not figure out any possible way.
The way a lamp will turn _off_ when feeding power is if the other side of the filament already has power. Staring at this schematic... I'm still suspicious of a "return" and "hot" mis-wire. It will cause the symptoms you experienced, but not sure how to actually set up the truck and trailer that way!
What color was the wire attached to the trailer connector? And/or the color you eventually connected _to_? Not worth going back under just to check - but if you remember maybe it will shed some light.
The PO must have bought this trailer connector from U-Haul. It's their kind of connector.
And must have wired it in, himself. Because he tapped directly into the truck wiring, instead of using that TEE that @Cubey has talked about.
Thing is, the wire going to the right turn signal on the truck, is yellow. The wire going to the left turn signal is green. This is the wiring on the truck. (I just looked up the wiring diagram. That IS the way this truck is intentionally wired from the factory.)
The wires on this connector, and on the trailer, and pretty much every trailer and connector, is opposite that.
Data point: This was never part of the problem. Since the PO had figured that out, and had at least wired the connector in, in the correct orientation, opposite the wire colors.
Since the wires coming out the back of this connector are potted in, I couldn't just switch the wires in the connector, so I have them swapped, when connected to the truck wiring. (Just as the PO had done.)
Everything works the way it is supposed to, so that is the way it will stay until someday when I decide to just replace everything with better wiring. (There is nothing as permanent as a temporary fix that works.)
PO had a piece of red wire connected to the end of the yellow wire on the connector, and spliced into the green wire on the truck. That red wire is very thin. And he intentionally cut away the insulation in a couple of places. Probably for testing. But never bothered to cover those places up.
For now, I just reinforced his splices with zipties. Taped up the cut off insulation spots and ziptied that tightly in place.
I used a piece of green wire, larger in gauge than what was on the connector, to tie the green wire from the connector into the yellow wire on the truck.
I am also using this for my third brake light signal, now. (Goes to the relay to open the relay, that powers the third brake light.) Which means the 3rd brake light flashes when the right turn signal is flashing. And doesn't, when the left turn signal is flashing. I don't really care about that. Cool thing is, though, if the hazard lights are flashing, then all 3 flash. And it still lights up as the 3rd brake light. 3rd brake light is essentially acting as a second right turn/stop lamp.
Then I just bunched everything up tight and ziptied it all out of the way where it won't get too much vibration and bouncing, or get caught on road debris.
And must have wired it in, himself. Because he tapped directly into the truck wiring, instead of using that TEE that @Cubey has talked about.
Thing is, the wire going to the right turn signal on the truck, is yellow. The wire going to the left turn signal is green. This is the wiring on the truck. (I just looked up the wiring diagram. That IS the way this truck is intentionally wired from the factory.)
The wires on this connector, and on the trailer, and pretty much every trailer and connector, is opposite that.
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Data point: This was never part of the problem. Since the PO had figured that out, and had at least wired the connector in, in the correct orientation, opposite the wire colors.
Since the wires coming out the back of this connector are potted in, I couldn't just switch the wires in the connector, so I have them swapped, when connected to the truck wiring. (Just as the PO had done.)
Everything works the way it is supposed to, so that is the way it will stay until someday when I decide to just replace everything with better wiring. (There is nothing as permanent as a temporary fix that works.
)PO had a piece of red wire connected to the end of the yellow wire on the connector, and spliced into the green wire on the truck. That red wire is very thin. And he intentionally cut away the insulation in a couple of places. Probably for testing. But never bothered to cover those places up.
For now, I just reinforced his splices with zipties. Taped up the cut off insulation spots and ziptied that tightly in place.
I used a piece of green wire, larger in gauge than what was on the connector, to tie the green wire from the connector into the yellow wire on the truck.
I am also using this for my third brake light signal, now. (Goes to the relay to open the relay, that powers the third brake light.) Which means the 3rd brake light flashes when the right turn signal is flashing.
And doesn't, when the left turn signal is flashing. I don't really care about that. Cool thing is, though, if the hazard lights are flashing, then all 3 flash. And it still lights up as the 3rd brake light. 3rd brake light is essentially acting as a second right turn/stop lamp.Then I just bunched everything up tight and ziptied it all out of the way where it won't get too much vibration and bouncing, or get caught on road debris.
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