electrical: night lights do not come on, but single/brake lights work [Archive] - RV Forums

ttchong

06-22-2007, 03:27 PM

Hello,
A brand new pop tent owner who needs some help. I'm a beginner (at best)!
we purchased a used 2004 jayco qwest 10k recently.
Once the trailer is hooked up, the turn signal and brake lights work.
However, the running lights (night lights?) do not come on when I turn on the headlights from the SUV.

I've read about grounding, it seems ok. Likely I'm not checking or doing something incorrectly. I've read and checked the fuse box in the SUV.

Any suggestion on how to go about checking or where to check?

- Thomas

tcwal

06-23-2007, 07:27 AM

Since the trailer's break lights and turn signals are working, you have a ground connection.

The most common problem I have encountered with trailer lights is corrosion of the connectors. Try cleaning both the vehicle and trailer sides of the connector with fine sand paper or emery cloth to get a shiny metal surface.

If that does not solve the problem; if you have or can get a simple test light, you can tell some about where the problem is. Disconnect the trailer electrical plug from the tow vehicle. Turn the vehicle running lights on. Now connect the ground wire of the test light to the ground wire of the vehicle plug (usually the white wire) or a good clean piece of metal on the vehicle frame. Now touch the probe end of the test light to each contact of the vehicle electrical harness.(If you have a seven pin connector, only test the outside contacts, the center connector is to charge the batteries and will always be hot when the tow vehicle is running.) The test light should go on when one of the contacts is touched. This will be the running light connection. If you have power on the vehicle side, there is a loose/broken wire or corroded connectiion somewhere on the trailer between the connector and the lights.

If the test light does not light at all, there is a problem with the wiring harness on the vehicle. Turn the running lights off. Turn on a turn signal. Use the procedure described to identify the contact for the turn signal. Do the same for the other turn signal and the brake lights. The remaining contact should be the running light contact. Trace the wire back from this connection to where the wire connects to the vehicles wiring and check this connection.
Some of the prewired harnesses that just plug into a plug in the vehicle wiring have a small box with some electronics inside, I had to replace the whole trailer connector harness when one of these failed.

If the problem appears to be on the trailer side, try cleaning the corresponding contact on the trailer connector again. If this does not work, check the bulbs. While it is unlikely, since the running lights are typically used more the one element in the bulbs may be burned out. Also check the contacts in the tail lights and on the bottoms of the bulbs for corrosion. Next look under the trailer to see if there appears to be any obvious cuts or scrapes on the wire to the tail light assembly. Check carefully around the holders that attach the wire to the trailer frame.

Hope this helps.

Good luck.