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Ask Dave: Why isn’t my trailer’s right turn signal working?

Dear Dave,
Any suggestions as to why my Coleman 2019 camper’s right taillight turn indicator is not working? I tried three different bulbs with no success. —Chuck

Dear Chuck,
To locate the problem with your turn indicator, I would start with checking the 7-pin connection at the truck or car to make sure you have 12-volt power coming from the tow vehicle to the trailer. You can do this with a multimeter, simple 12-volt light tester, or pick up a handy device from almost any auto part store such as this one from Amazon.

I have had several situations where a fuse in the main 12-volt fuse block of the tow vehicle has blown due to a temporary short in wiring or even moisture getting into the plug.

Once you verify the wiring is good to the 7-pin connection, you will need to look at the turn indicator fixture itself. You should be able to use a multimeter and pull out the bulb and test for power at the points of the fixture. You might even want to take the fixture out and check the wiring to the back of it.

It may be a loose or broken wire to the turn indicator

If you do not have power to the fixture, it most likely is a ground wire that has become loose or broken. I would then take the fixture off and bench test it by putting a known 12-volt power supply to it. You can go directly off the house battery with a dedicated positive and negative wire to the fixture. If it works, then you know there is an open or broken wire leading to the fixture and you need to start from the shoreline cord and follow the wires.

Typically the culprit is a broken wire underneath the rig. Most trailer manufacturers run the thin wires along the underside frame and they are exposed to road debris and rocks getting kicked up. Sometimes it is easier to just run new wires.

If the fixture does not work with dedicated wires, then it is in the housing of the light fixture and typically it’s easier to just swap out the fixture. You might not be able to find an exact match, so I typically replace both so they look the same.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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JohnM
26 days ago

It has happened to me twice. Once on my Chevy 2500HD and once on a friend’s GMC 1 ton diesel that the small fuse on the truck’s huge fuse panel had blown. Individual fuses for each trailer turn signal light. Who knew?

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