Magnetic Tow Lights Dim with Multiple Signals

Updated 10/25/2018 | Published 10/24/2018

Question:

Ive been trying to help my buddy with his trailer light issue. His blinkers work correctly if nothing else is turned on. If either his brakes or running lights are on, then a bulb on the opposite side from the bulb that is blinking, goes dim. In other words, when the left blinker is on, the right running light and or brake light goes dim and vice versa. This happens with both the new lights he installed on his Jeep dedicated tow lights and external magnet mouted lights. Both the magnetic lights and the Jeep installed light systems are new. I assumed the problem was with the wiring on his motor home. I installed a set of relays, and ran dedicated hot and ground to both of the trailer light wiring looms so that the relays were only switching the power going to the lights - still had the issue. Finally, I connected the magnetic lights to MY vehicle and they do the same thing! We tried them on a total of 5 different vehicles and they do the same thing on all 5. Then we tried my magnetic lights on two different vehicles mine are the same brand as his and they also do the same thing. Its subtle, not real obvious, but it does occur. So, now Im thinking that the ground wires used with these lights may be too small to carry the load of more than a single light. Note that these are NOT E-trailer light systems. I told my buddy who doesnt live close by to try a larger ground wire and if that doesnt correct it, then to try replacing all of the wire with heavier gauge. The wire is VERY small gauge 18 gauge or thinner. Do you think I am going in the right direction, or barking up the wrong tree?

asked by: Paul

Expert Reply:

It doesn't sound like to me that there is anything wrong with the lights or wiring. We have this complaint about magnetic lights quite often and there usually is nothing to blame. The turn signal and brake light are both carried through the same dual filament bulb. The circuit associated with the brake/running lights will generally be brighter than the circuit for the turn signal but this could vary depending on which circuit has the initial inrush of power. If you test each circuit directly before it reaches the bulb with a multimeter you can confirm the above hypothesis.

I do not think it would hurt to run a larger gauge wire but I recommend just switching to a set of magnetic tow lights with separate brake and turn signal bulbs like the Split Lens Magnetic Towing Tail Lights part # SPL30B-6. You will also need an adapter like part # 47549 to use them with the 7-way on your motorhome.

expert reply by: Conner L