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Testing Operation of LED Magnetic Towing Lights  


I purchased some magnetic led towing lights and they don’t work. I tried them on another truck and they didn’t work. I tried another and they didn’t work either. Both truck 4 pin hook ups work on other trailers. Is there a difference in the voltage or what could be the reason they don’t work? Thanks


Helpful Expert Reply:

The Hopkins Magnetic Tow Lights # C6304 you referenced require you to install 8 AA batteries in order to function so this is the first thing to check.

LED lights of any type are generally highly electrically efficient. LEDs typically use about 1/10th as much power as an incandescent light.

This high efficiency can sometimes "fool" certain vehicle's trailer wiring systems. In certain cases load resistors like # DI34ZR can be needed to mimic the higher power draw of standard incandescent bulbs. They soak up some power so that the wiring system can detect the LEDs.

The best way to test the lights on their own is with direct battery power from the vehicle battery or from a well-charged spare battery if you have one around. A set of jumper cables and two short lengths of wire make it easy to test. Connect one end of the jumpers to the lengths of wire and the other to the battery terminals. You now have a ground and hot wire lead you can apply directly to the magnetic light's 4-pole ground pin and, one by one, to each of the three light circuit contacts. Please refer to the linked photo.

If the LED towing lights do not function with this direct battery power then they are bad or they have a damaged plug. If they do function then you know the issue is compatibility with the specific wiring systems on the vehicles.

If you happened to have lights that require 24V operating power then this would explain the problem with using them with a 12V system. Most such products are labeled with their required operating voltage.

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