JustinID

I just wired up a 4 wire harness for my little race tire trailer. It's behaving kinda funny and sometimes blowing fuses. The left light is somewhat intermittent in working Sometimes it won't turn on when braking and I think it didn't turn on the turn signal once. But other times it's just fine. Also, it's not just the trailer light, it's the car's left tail light as well. If one works, they both work. If one doesn't work, neither work. The right side brakes and turn signal work just fine. I'm getting ready to just say screw it to that and deal with it being funky.

The other problem I'm seeing is that I'm blowing the 20amp tail light fuse every time I turn on the running light or head lights. I don't understand why the brake lights can work, but only the running lights would blow a fuse. They both have 20 amp fuses and I would think that the brake lights would actually draw more power.

I hooked up a multimeter to a ground and to the light side of the tail light fuse holder (with no fuse installed) and learned that despite having a degree in computer engineering, I still can't figure out crap about analog circuits. With nothing turned on but the parking lights, and the tail light electrical plug (at the back of the car) unplugged, I'm seeing 0.7 ohms. That implies a 17 amp draw with the tail lights completely unplugged. Now if I turn on the headlights, the resistance drops to 21.4 ohms. Why would turning on the headlights effect the draw across the tail light circuit? Especially when the tail lights are unplugged??? If I turn the ignition on, then the that effects the readings as well. Plugging the lights in makes the resistance drop (potential load goes up) which makes sense, but why wouldn't there be no load if the lights are unplugged? This stupid car makes no sense to me. Or is it, this car makes no sense to stupid me. :banghead:

FWIW, despite the ohm readings that I can't make heads or tails of, the car does NOT blow fuses when the trailer is not attached.

In the end, I'm left wondering if the trailer is just drawing too much current and that 20 amp fuse can't keep up. I know it's normally a no-no... but what about just trying a larger fuse? 25 or 30 amp? If I can't get this going, I have no clue how I'm going to get power out to my trailer.

Someone please save me before I rip out what's left of my hair.

WhiteBird00

iTrader: (4)

On a Firebird, connecting a 4-pin trailer harness is straight forward. Green goes to dark green on the right taillight. Yellow goes to yellow on the left taillight. Brown goes to brown from either side. White goes to ground (black wire in the taillight harness will work). If you have the connections made that way (and you've tested at the trailer plug) but you still have problems then the problem is in the trailer wiring. You should not blow a fuse by just adding one additional tailllight (the trailer's) on each side of the circuit. You might find that the turn signals flash erratically if you still have the factory thermal flasher - an inexpensive electronic flasher will solve that problem.

FYI, late model Camaros can't use a 4-pin trailer harness without an adapter to combine the separate turn signal and brake signals onto a single wire for each side.

JustinID

I did more extensive testing and believe that there is a short in the trailer. I removed all the light bulbs and the two brake/turn-signal lines are now completely disconnected (infinite resistance to ground). The brown running light wire is still showing 0.9 ohms even though it should also not be connected to anything. I'm about to start pulling the wire out of the trailer so I can more thoroughly inspect it. If I still can't find it, I'll have to start cutting and resplicing it to narrow down where it's shorting out. If I still can't get that to work, I'll probably have to just rewire the whole thing.

Regarding the wiring adapters, I actually have one of the 5 to 4 wire adapters. It took me about 30 minutes of scratching my head, reading my service manual, and searching the web to figure out I actually didn't need it.

JustinID

I found the problem. The person I bought the trailer from had added a bar across the back to allow the trailer to be stored on end. When he tightened that down, he pinched the running light wires in a frame bolt. That broke the insulation and gave me my short. I got the wire unpinched, taped it up, and now it's all working fine.

I forgot to mention, regarding the blinker, I replaced mine a few years ago because it had gone bad. The one I replaced it with seems to handle the trailer just fine and my blinking speed is normal with and without the trailer attached.

Thanks for the help.