Rear Light Problem

[wingbone]

When hooking up lights, how do you keep the L and R lights separate from both activating. This is actually on my dump truck but they have the same exact lights on both. It says to hook up the turn signals and brake light to the same wire (red on the lights), but how do you keep it from activating the other side if both turn signal wires are also inline with the brake wire? I know I'm overlooking something obvious.

 

[George2615]

I don't know what dump truck you have so can't comment on your wire color but for basic trailer (lighting only) wiring you need to hook up 4 wires. left turn, right turn, parking lights, and ground. Trailers with brakes require more wiring and a brake controller in your truck.

You'll need to install a trailer plug on your truck. Then you'll need to connect the plug wiring to each of the above. If your not electrically inclined most any garage mechanic can hook it up for you in less than an hour. I've attached a file showing the standard 4, 6, and 7 pin color coded plugs. Brake light signals are sent through your turn signal wiring.

 

[Skyco]

That doc shows black for tailights on the 4 pin, it should be brown.

 

[wvpolekat]

The brake lights should not be tied to each other. They are 2 separate circuits. At least at the trailer. So, when you put your brakes on, both turn signals light up. You don't actually wire "brake" lights to the trailer, just turn signals, the vehicle takes care of which one is doing what.

 

[wingbone]

I haven't even gotten to the trailer plug yet. I need to isolate my L/R tail lights on the truck and I guess subsequently this will allow me to hook up my plug. The lights on my truck are just like regular, round lights that slip into a cutout circle with rubber ring. They have a white, red, and black wire. The white is the ground, red is brake/turn, and the black is tail or running lights. The problem is, I'm supposed to hook up the brake wire from the truck to the red wire on the lights. This powers the brake lights fine. However, the red wire on the light is also for turn signals. When I hook up those, this is now sending flasher/turn signal power to both lights since they are also hooked to the brake light wire. How do I isolate the turn signal from powering both sides. Do I need to use diodes in some form or fashion?

 

[wingbone]

The brake lights should not be tied to each other. They are 2 separate circuits. At least at the trailer. So, when you put your brakes on, both turn signals light up. You don't actually wire "brake" lights to the trailer, just turn signals, the vehicle takes care of which one is doing what.

Yeah, this is really the problem I'm having and I was explaining further in my post while you were posting this. The truck at one time probably handled this upfront but I'll probably catch the devil trying to figure out where.

 

[Diamondpilot]

You will need a tail light converter. Takes 5 wires in and converts them to 4 wires out. They run $15 or so and will take care of you.
The 5 in are R Turn-L Turn-Brake-Ground-Running


The 4 out are Right-Left-Running-Ground


Chris

 

[wingbone]

Thanks, Chris.
I might actually be lucky and you might be able to give me a little more help. I had bought a used trailer hitch for my Chevy Uplander which came off of a Chevy Venture. This also came with a Curt wiring Harnes from the Venture. Well the hitch was the same but the wiring harness did not match. I believe I might be able to use this as the converter. It has 5 wires going in: White/Brown/Yellow/Red/Green. Coming out to the trailer side is White/Brown/Yellow/Green. I'd bet a million dollars this is doing the same thing. Would you suspect brown to be running lights and red to be brakes? Yellow and Green turn signals?

 

[wingbone]

Well, that thing I had didn't work. I really don't see why it wouldn't. It would allow the tail light(brown wire) to power the light both ways which makes sense. It seems like the other would have worked too and I tried it from both ends with a battery.

 

[Diamondpilot]

You need a converter. Get one at WalMart or any Uhaul. Simple hook up. It has a box with electrical components that are like magic to me but its what you need if I am understanding you correctly. Many newer vehicles need them so you are not in new territory.

Chris

 

[wvpolekat]

You need a converter. Get one at WalMart or any Uhaul. Simple hook up. It has a box with electrical components that are like magic to me but its what you need if I am understanding you correctly. Many newer vehicles need them so you are not in new territory.

Chris

Correct, we had to get one for my wife's trooper. The determining factor is if it has separate brake and turn bulbs. I assumed that a dump truck would not, but apparently, that is not the case.

The one you have may work, but you would have to get a schematic and track down the wire colors.

 

[wingbone]

You need a converter. Get one at WalMart or any Uhaul. Simple hook up. It has a box with electrical components that are like magic to me but its what you need if I am understanding you correctly. Many newer vehicles need them so you are not in new territory.

Chris

I went to Walmart and bought a converter and it didn't work either. It's doing exactly the same as the unit I already had; running lights work through it but the brakes/turn signal do not. I can circuit test my individual wires coming from the truck and they work fine, but not when ran through the converter. I even tried an experiment with both the unit I already had and the new one from Walmart completely separate from the truck. Here's what I did:
I had a small gel cell 12v battery that I used to hook directly to the individual wires on the harness. I had a 4 wire connector coming out the other side of the harness hooked directly to an extra, new trailer light I already had. The running light worked just like on the truck but the others would not do anything. This experiment is completely away from the truck done on a table. I tried all combinations of hooking the red/green/yellow wires individually and together and could not get them to do anything. Still only the brown running light would work in this manner. I don't know how much simpler it could get than doing it like this.

 

[aczlan]

I haven't even gotten to the trailer plug yet. I need to isolate my L/R tail lights on the truck and I guess subsequently this will allow me to hook up my plug.

You do not need to isolate the Stop/Turn lights for the trailer, they are both on the same wire in the trailer plug on any 4, 5, 6 or 7 pin plug I have used.

The switching between brake lights and turn signals is handled at the front of the truck, so the lights use the same filament for brake and turn lighting.

If you are hooking up a 4 pin flat plug you have (starting with ground) Ground, Running/Marker/License Plate lights, LH Stop/Turn lights, RH Stop/Turn lights. (see here for a diagram)

Thus the wires on your truck are good to go as-is


Aaron Z

 

[aczlan]

I had a small gel cell 12v battery that I used to hook directly to the individual wires on the harness. I had a 4 wire connector coming out the other side of the harness hooked directly to an extra, new trailer light I already had. The running light worked just like on the truck but the others would not do anything. This experiment is completely away from the truck done on a table. I tried all combinations of hooking the red/green/yellow wires individually and together and could not get them to do anything. Still only the brown running light would work in this manner. I don't know how much simpler it could get than doing it like this.

You would need to hook the negative wire (normally white) on the harness/adapter to the negative terminal on the battery, then you should be able to hook up the others up to the positive terminal one wire at a time and they should turn on.

Aaron Z

 

[wingbone]

You would need to hook the negative wire (normally white) on the harness/adapter to the negative terminal on the battery, then you should be able to hook up the others up to the positive terminal one wire at a time and they should turn on.

Aaron Z

Aaron,
I did have the white wires grounded to the negative terminal. I had it grounded like this and the brown wire/running light worked fine. I'm assuming the running light is a simple pass through on the harness and this is why it's working. The others I can't get to work.

 

[aczlan]

Aaron,
I did have the white wires grounded to the negative terminal. I had it grounded like this and the brown wire/running light worked fine. I'm assuming the running light is a simple pass through on the harness and this is why it's working. The others I can't get to work.

So the converter is not working?

As I understand your situation you should not need a converter because your stop and turn lights are on the same wire. You would only need a converter if (like on my Volvo 940) you have separate turn and stop lights, which (from your description) I don't think you have.

Aaron Z

 

[wingbone]

Aaron,
They are not on the same wire on the vehicle, but regardless, I just went outside and tried my bench experiment again and used a multimeter. If I hook the brown wire(running lights) to the battery and check with meter or hook to a light, it works fine. I can even hook the white wire to the battery and get voltage on the other end because it is a simple pass through just like the brown wire. But when I hook the red, green or yellow to the positive side of the battery and then try to check for voltage or hook to a light, I get nothing. I even tied the red and green wire together which would be like applying brakes and using a turn signal at the same time but nothing. Seems like if I hook a battery on one end and test right on the other end I should get something and it's so simple, I can think of any other way to try to hook it up to even test it.

 

[aczlan]

I haven't even gotten to the trailer plug yet. I need to isolate my L/R tail lights on the truck and I guess subsequently this will allow me to hook up my plug. The lights on my truck are just like regular, round lights that slip into a cutout circle with rubber ring. They have a white, red, and black wire. The white is the ground, red is brake/turn, and the black is tail or running lights.

They are not on the same wire on the vehicle

Perhaps I misread your posts, I was going off of the first post quoted above, which (as I understand it) says that each taillight has 3 wires which are used as follows:

• Left light
  1. Ground (TW) White on Truck
  2. LH Stop/Turn (TLST) Red on Truck
  3. Marker (TM) Black on Truck
• Right Light
  1. Ground (TW) White on Truck
  2. RH Stop/Turn (TRST) Red on Truck
  3. Marker (TM) Black on Truck
• If the truck is wired as such I would connect the above wires to a 4 pin flat trailer plug as follows(the abbreviation in the first parentheses matches the wire ID from the above lists)
  1. Ground (TW) (White on truck to White on trailer plug)
  2. Marker (TM) (Black on truck to Brown on trailer plug)
  3. LH Stop/Turn (TLST) (LH Red on truck to Yellow on trailer plug)
  4. RH Stop/Turn (TRST) RH Red on truck to Green on trailer plug)

Is the truck wired like I listed above? if it is, you do not need a light converter, you can hook the trailer right into the truck light wiring.

Seems like if I hook a battery on one end and test right on the other end I should get something and it's so simple, I can think of any other way to try to hook it up to even test it

Do you know for sure that this converter works? it sounds like you are testing it properly.

Aaron Z

 

[wingbone]

The converter is brand new and I've actually tried another I scavenged from on old Chevy Venture harness. My truck lights are the exact same lights as my trailer lights.
White=Ground
Red=Stop/Turn
Black=Running lights

Truck has individual wires for:
Stop
Left Turn
Right Turn
Running lights

My original problem was how do I hook the truck's stop light wire to both lights without having them bridge when either turn signal is used. This is when Diamondpilot told me I needed the converter, which makes sense to me. I tried the harness I already had and couldn't get it to work so I thought maybe it just wasn't designed to do what I wanted to do. I went to Walmart and bought a 5 wire to 4 wire converter that is supposed to do exactly what I'm looking for, but it behaves exactly like the harness I already had. This makes me think that it isn't just a bad unit since they are doing the same thing. I guess I'll have to take it back and exchange it for another just to see. I'll test the next one with a meter before I ever hook it up to any power source.This seems like it should really be an ultra simple task, but maybe I'm doing something stupid.

 

[Diamondpilot]

I am at a loss. Try another converter, maybe this one is bad, or its time to take it to another set of eyes. Hard to fix on paper.

Chris