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wats218
07-21-2009, 07:34 AM
So when we bought the trailer, none of the lights worked. Replaced all the lights and they acted weird. Figured it was a ground issue. Since the inside of the trailer was pretty rusted, I figured that it wouldn't be a good ground, so I ran a separate wire and connected all the grounds together and then connected them to the 4-pin connector. Check the truck sound ground and it looked pretty clean. After doing this, the lights still operate weird. When the trailer lights aren't connected to the truck, the truck signals work fine and the output is correct. The truck is a 7-pin round and we convert it to a 4-pin flat. When they are connected, here's whats happening.

Tail Lights - work fine
Head Lights - don't work (not sure which are suppose to light up (tail, right, left))
Flashers - work fine
Right Signal - shorted out (truck signal blinks rapidly, nothing on the trailer lights)
Left Signal - shorted out (truck signal blinks rapidly, nothing on the trailer lights)

I couldn't understand why the hazards work, but the turn signals don't work individually. Thought it might be that the right and left wires are shorted together. Tested each without the other connected to anything and they were still shorted. Even tested them with both connected to the same signal from the truck and they were shorted. Does anybody have any ideas on what this could be? I thought trailer lights would be a simple fix, but I have no clue what else it could be. Could it be that the flasher in the truck isn't strong enough? Could I still have a weak ground? Any help is appreciated. Thanks.

wats218
07-21-2009, 12:28 PM
bump...just bought an electronic flasher. going to try it tonight.

mayo93prostar
07-21-2009, 12:40 PM
I suggest testing the trailer seperate from the vehicle with a battery or a battery charger as the power source. some wires with alligator clips help this. connect ground to ground and then feed one of the 3 pins on the 4-pin flat connector with the positive lead to test each circuit seperately. you will measure a short to ground on each light circuit because the lightbulb element provides the electrical path. Another suggestion is to buy a DC test light to test the 7-pin circular and the 4-pin flat output. what about brake lights? some vehicles have turn signals in yellow seperate from brake lights in red. these should be converted to a trailer interface into the 7-pin round connector. my chevy truck has the seperate turn/brake lights but the trailer lights work fine with the 7-pin round to 4-pin flat connector. some vehicles require an adapter to do this.

wats218
07-21-2009, 01:01 PM
I did test the trailer this way when I originally replaced the lights, only because I didn't have the truck available to hook it up to. I'm pretty sure that everything tested out good this way. I will verify again tonight. That's why I was stumped when I actually connected it to the truck and it didn't work. Thanks.

Ski-me
07-21-2009, 01:12 PM
What kind of truck? Is the wiring harness from the factory or aftermarket (self-installed)?

If you have a blinker bulb (orange or red) in the rear and also a separate brake light bulb, you need a special trailer brake converter to combine those signals into the flat 4 bar.

In other words, the brake (bright light) and blinker (bright light) need to be combined together to allow the 4 bar to work correctly. If they are not, you get signals fighting each other and your vehicle blinkers flash rapidly.

We had this on our Jeep Grand Cherokee (94').

wats218
07-21-2009, 01:24 PM
It is a 94' F150. I'm not sure if the vehicle wiring harness is after market or not, but I tested the output from the 4-pin flat, and it seams to work fine. When you hit the brakes, the tail light terminal has voltage, and when you put each turn signal on, the correct turn signal terminal has voltage. Its only when its hooked up to the trailer that it goes hay-wire. I'm not sure if it is a wiring problem in the trailer, bad ground, or an overload on the flasher. If I take the left turn signal and right turn signal wires out of the 4-pin flat and contact them together without the trailer connected (just the harness) it acts the same is it does with the trailer connected. These two wires, however, are only near each other in the tongue of the trailer, since they both run down the opposite sides of the trailer afterwards. I find it unlikely that these two wires are contacting each other in that short stretch (only about a foot that I can't see).

Jerseydave
07-21-2009, 02:18 PM
Sounds like you need that heavy duty (electronic) flasher for your turn signals. The hazard flasher is most likely heavy duty already, that's why they work and the turn signals don't. A flasher that is not heavy duty will make signals blink very rapidly every time.

BTW, when are you coming up to the river for some skiing??? :)

wats218
07-21-2009, 02:30 PM
I'm hoping that's the problem. Went to pepboys and they didn't have a heavy-duty flasher, but I read that an electronic flasher will work since it isn't based on the resistance of the circuit. Keeping my fingers crossed.

I'm on vacation next week, taking the boat to Lake Harmony. Hopefully we'll be able to make it one weekend in August...running out of summer. I'll hit you up if we can nail down a weekend. What exit off 295 is it?

mayo93prostar
07-21-2009, 02:31 PM
wats, you said "When you hit the brakes, the tail light terminal has voltage,..." maybe you mispoke but if this is true, something is not wired correctly. the tail light terminal should have voltage when the tail lights and/or headlights are on. both turn signal terminals should have voltage when the brakes are on. I know these things can get frustrating. good luck.

mayo93prostar
07-21-2009, 02:32 PM
double check that what you check independantly lines up on the same connector pin on both the truck and the trailer. just another thought.

wats218
07-21-2009, 02:51 PM
both turn signal terminals should have voltage when the brakes are on.

I'm confused...why is that? Isn't the voltage what powers the lights?

Jerseydave
07-21-2009, 02:52 PM
I'm hoping that's the problem. Went to pepboys and they didn't have a heavy-duty flasher, but I read that an electronic flasher will work since it isn't based on the resistance of the circuit. Keeping my fingers crossed.

I'm on vacation next week, taking the boat to Lake Harmony. Hopefully we'll be able to make it one weekend in August...running out of summer. I'll hit you up if we can nail down a weekend. What exit off 295 is it?

^exit 52, head west toward Florence, cross over route 130, follow Delaware ave for 1.5 miles to ramp on right. Can't miss it.

Double check your wires, here's the way they should be:
green-right signal and brake light
yellow-left signal and brake light
brown-running lights (tail lights)
black (or white)-ground wire

If you have a folding tongue, make sure the wires are not pinched/bare/touching each other. I'm betting my money on the flasher being too weak though.

wats218
07-21-2009, 03:09 PM
thanks for the directions.

Thats how all the wires are. I'm really hoping its the flasher. My uncle tows a camper with his truck. I might try and see if the trailer works hooked up to his truck.

wats218
07-22-2009, 07:09 AM
Put in the electronic flasher last night and now everything works. Thanks for the help.