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Troubleshooting Turn Signal Not Working on Trailer  


The right hand rear indicator will not work on my old 1978 Millard It was dull like really dull so I got a new set of led lights to Replace them However I can not get the right indicator to work Everything else works I even replaced the whole wiring from front plug To the back not even using the old internal wiring Still nothing What have I missed I will say I haven’t had the towball/hitch on the vehicle when testing but that shouldn’t matter when everything else works really well


Expert Reply:

I can give you some troubleshooting steps to take to try and find out what is wrong with your turn signal. In order to determine the specific problem you will need to purchase a circuit tester if you do not have one - the very handy Cordless Circuit Tester # PTW2979 would be my strong recommendation due to how easy it is to use - and test the connector on your vehicle after disconnecting it from your trailer. Check the wiring going into your harness from your tail lights to see if the turn signal wire is carrying a signal, if not then the issue is with the vehicle wiring.

If the signal going to your harness is okay, you'll need to test the signal coming out of the harness, and if it is correct then your issue is likely going to be with the trailer side wiring. You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you are going to need to either replace the plug or clean the corrosion. You'll also need to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion.

Finally, check your wiring thoroughly to ensure there are none that are crimped, broken or otherwise damaged. I have added links to a pair of help articles on trailer wiring, including a troubleshooting guide which I highly recommend taking a look at.

expert reply by:
Kyle S

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