Why Trailer Wiring Carries Low and Higher Voltage on the Light Circuits

Updated 09/25/2012 | Published 09/24/2012

Question:

i tapped into the lights like instructed, when i put the headlights on the tester shows low voltage on both left and right prongs for the brakes and turn signals without them being applied once applied all shows strong on the tester?? please help

asked by: Alex

Expert Reply:

What you are describing is normal. When you turn on your headlights the running lights of your trailer should illuminate. The running lights are dimmer than when the bulb is being used as a turn signal or a brake signal.

Basically the trailer lights use dual intensity bulbs that when the lower amperage is used (like running lights), the bulbs illuminate, but when a higher amperage is used (like brake or turn signal) they illuminate brighter.

So unless I have misunderstood you, everything should be working fine with the trailer connector you have installed.

expert reply by: Jameson C