Lights dont work properly

[Scott D]

Ok, here?s my problem. I searched the web and found nothing, so now I?m asking the experts; hopefully some one can help me.
I did some fabricating to my boat trailer and in the process I converted all the incandescent lights to LED?s. (Two tail lights, three light marker in the center rear trailer and eight marker/parking lights, four on each side of the trailer)
Now when I connect the trailer to the H3 (Hitch& lights) and turn on the parking lights they all turn on. I when I apply the turn signal (right or left) nothing happens to the trailer lights until I turn off the parking lights then the lights flash, but all the parking lights flash on which ever side you apply the turn signal. When I turn off the parking lights and apply the brake all lights come on (parking and tail) same thing happens with the Hazard lights.
I?m pretty sure every thing is wired correctly, all parking lights were wired to the brown wire, right tail light to green wire, Left tail light to yellow.
The trailer has a standard four wire flat plug. I checked all the wiring and it seems ok, I did run out of day light so I have to go over it again tomorrow morning.
Now I?m no expert, but I do have some experience in wiring 12 volt lights. I wired my utility trailer and my grandfather?s two utility trailers no problem. I?ve added parking lights (LED?s) to my Ford Super Duty that I used to own, no problem. When I was a teenager I used to wire my uncle?s tow trucks that included many Paring lights, Flood lights, strobes and light Bars to include relays, lets face it It?s not rocket science, but I?m really racking my brain on this one. Also when the lights flash they flash really really fast like those Euro cars.
The H3. It did not come with a towing package. So I purchased an after market hitch and had it installed along with a four wire flat connector. Now the wire connector they added says U-Haul on it. The trailer place I went to is not a U-Haul place but they are an authorized dealer so that explains the plug. But the plug looks like a double four flat. 4 on top and 4 on the bottom. My trailer connector will only fit the bottom 4 connector on that U- Haul connector. Now it did cross my mind that the U-Haul plug might be the culprit. The wires were spliced into the Hummer. I haven?t checked to see if the trailer place wired it correctly. Also I know that U-Haul uses weird adaptors that you have to buy separate when you rent one of there trailers.

• Do you think that could be it or did I mess up some where in the trailer wiring like something is not grounded correctly or a bare wire?
• Am I overloading the H3 with the trailer lights?
• Why do the flash so fast?
• Do I need to add some kind of adaptor for the LED lights?

Any help or ideas would be great. I will be losing sleep over this tonight trying to figure this out. I know it?s got to be something very simple. Thanks.

[Michael1]

Scott,

The first place I would look is your ground. Also do any of the vehicle lights do funny things while the trailer is connected?

Is this the only trailer you have connected to your H3? If so, I would take a test light or voltmeter, and connect it to the Uhaul connector on your truck to be sure they wired it correctly.

Good luck!

Michael

[f5fstop]

No time to really think this through, but I will say that the BCM controls the rear signal lights and park lamps, so something is causing the BCM not to flash. In additon, hard to say what might be wrong without seeing the actual wiring diagram for spliced in connector and the trailer lights. LEDs could be a problem, but not thinking that at this time.

[fourfourto]

Did you use the wire cluster at rear bumper to hook up trailer lights or did you splice into taillights?.
I read a post about problems with the LEDs .I dont rememember the outcome.

[f5fstop]

Sounds like the harness is wired correctly into the correct wires. What type of bulbs (or LEDs) are on the trailer?
When you say you turn on the signals and nothing happens to the trailer lights (no flashing) do the lights on the H3 still flash?
As I stated earlier, the BCM controls the left and right turn signal/brake lights all on one circuit.
I don't know what to tell you without seeing the wiring after the splices such as the U-haul wiring to the connector, and from the connector to the trailer. You could check for voltage at the connector. With park lamps on, power to the green/yellow wires, but when one of the turn signals is activated, the wire to that side of the vehicle should pulse on/off.
Are the LEDs designed for direct replacement for a 12-volt bulb? (These should have enough resistance built in to compensate for the 12-volt bulb that is not being used.) When you say the flashers flash fast, it almost sounds like the BCM senses a dead bulb somewhere in the circuit.
Wish I could be of more help, but long distance diagnosis is pretty difficult.

[Scott D]

Well here's what happened today. I took Michael 1 advice and checked the ground, which made good sense. I pulled out my handy dandy grinder and put my sanding wheel on and sanded every single lights ground down to the bare metal on both sides to include the ground wire on the wiring harness with no change to my problem.
So I checked every single light to make sure it was wired correctly, and they were. Now I started to turn my anger and frustration to the U- Haul connector . I checked it once, twice even three times just to make sure because by this time I was starting to dout myself. It turns out the U-Hual connector was wired correctly and working like it should.

And to answer your question Fourfourto the connector was spliced into H3?s wiring harness. And your question F5fstop, the lights on the H3 work fine nothing funny. About the fast flashing the burned bulb theory did cross my mind, but I was leaning more toward the short in a wire theory because in my experience a burnt bulb would not flash just stay on. But that theory was not looking good either because I wasn?t blowing any fuses or burning out any lights, but it was a good idea. Oh and yes all the LEDs designed for direct replacement for a 12-volt bulb. Michael 1 my Utility trailer and my grandfathers trailers are all 6 round connectors so I couldn?t go that route.

So now I was out of ideas and options and dreading what I had to do next. Rewire the whole trailer. By the way the trailer frame is boxed. So there I go to the trailer shop and pick up 30ft of wire. On the way home I stopped by U-Haul and asked if I needed one of those special adaptors just to make sure, anything not to rewire the whole trailer, and the guy told me no not for what I had. I was ready to hook up directly to a four flat, Damm.

Once home I started gutting the trailer wire and what do you think I found. Yep, bare wires. I even found wires melted together. It seems like I located my problem. Apparently what happened is when I was doing my fabricating the Acetylene torch heated up the frame to where the wires in side the frame melted. I guess 2000 F will do that. I was super careful when I was welding to keep the splatter to a minimum to protect the exposed wires but never occurred to me about the wires inside the channel while using the torch. Well I guess I learned the hard way. I know for next time.

Needless to say I wired every thing up and all the lights work as the should. And the fast flashing is gone. Lights flash normal as they should. Which brings me to a question for F5fstop. I went to the auto parts store and tried to find a heavy duty flasher because before I knew about the bare wires I thought I had I weak flasher. Well nobody could find the darn thing. Not for a H1, H2, or H3. No flasher module seems to exist for the Hummer. I looked in the owners manual found nothing. So is the flasher some where other than the fuse block or is it controlled by the computer?

Any way I was pretty impressed that even with a short in the system I didn?t blow any fuses in the H3 or LED?s on the trailer and I still had running lights. With regular incandescent lights I would have blown many bulbs and fuses. I guess you could think of it as a safety feature for night time driving till you get home to fix the problem. Seems like LED?s are pretty durable.

Now that I had every thing working properly I yanked out that U-Haul plug and replaced it with a 7 round plug and put a 6 round receptacle on the trailer and everything works beautifully.

Well thanks to every one who chimed in to help me out. This site is great, lots of good info and great people.

[f5fstop]

Remember, the BCM controls the flashers
There is no flasher module. The BCM sees an input from the turn signal or hazzard switch, and turns the correct bulbs (front and back) on/off.
By the way, the bulbs or LEDs had nothing to do with you not blowing fuses. If you had direct shorts to ground with a power wire, the bulbs mean nothing. In addition, you said you had direct 12V LED replacements, so they had built in resistance to emulate a 12V bulb, to prevent a fast flash due to low resistance.
The new BCMs have some decent protection against shorts to ground.

Glad to hear it is fixed.

[Michael1]

Originally Posted by f5fstop

Remember, the BCM controls the flashers
There is no flasher module. The BCM sees an input from the turn signal or hazzard switch, and turns the correct bulbs (front and back) on/off.
By the way, the bulbs or LEDs had nothing to do with you not blowing fuses. If you had direct shorts to ground with a power wire, the bulbs mean nothing. In addition, you said you had direct 12V LED replacements, so they had built in resistance to emulate a 12V bulb, to prevent a fast flash due to low resistance.
The new BCMs have some decent protection against shorts to ground.

Glad to hear it is fixed.

No, no!!! There HAS to be a flasher module! I can hear it tick tocking under the dash when the signal's on.

[sltbluh3]

well I cant help your problem but I have something along the same line. I have a trailer that I bought back in 2002 I usaully pull it with the Olds bravada lights work fine. Hook the H3 up and as soon as I plug the 7 prong connector in the parking lights on the H3 comes on even though it is not running and the keys are out of the ignition. any ideas? all lights on the H3 work and all lights on the trailer work?