I officially hate wiring cars and trailers. I got the car wired up. I used one of those circuit testers with the light in the handle. Every thing works at the 4 connector at the car every thing works on the wires 5 inches from the trailer side of the four connector. Yet no trailer lights. I pulled the cover on the trailer lights(they are brand new) the bulbs are good and when I used the tester I had power, however it was much dimmer then at the back of the car. Whats my problem? The trailer is 17 ft long and I figure I have approx 20+ feet of wire. Is it possiable that I don't have enough power? I would think that the trailer light bulbs would be at least dim but I get nothing. Any ideas guys?
The Car is a 1995 subaru legacy Wagon.
Forget using a test light or circuit tester. They don't tell you much of anything. Use a digital volt meter. Check the voltages at the lamps. You probably have resistance in the circuit somewhere. Try having the car's engine running to see if the lights are bright. You need to find where the problem is by measuring voltages at different places. The problem may be with a poor ground circuit if all lamps are dim. Try measuring voltages at the lamps with the meters ground lead on trailer's ground connection and on the car's ground point. If the voltage is higher when grounding on the car, then you have a poor ground from the car to the trailer or through the trailer's ground circuit.
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sparky
What is the gauge of the wiring? Don't use household wiring either. Bad connections are also suspect here. As for the light bulb test probe, get rid of it and get an auto-ranging multimeter (about $25) The light bulb test light can fry your electricals if you happen to probe into the wrong wire (direct short). We highly recommend that you use at least 10 gauge multi-strand wire to connect the lights.
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Never send your ducks to eagle school.
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How did you hook up the ground side of the circuit? As others have suggested, you have a connections issue. I would make this observation however; if you decide to use a voltmeter, and you read something like 12v at the taillight, try using the test light while measuring voltage.. the problem with the voltmeter is that it doesn't load the circuit and can give you false readings that send you off chasing problems that don't exist.
Jim