Forum Discussion

Dragonfly's avatar
Dragonfly
Explorer
May 19, 2014

TRUCK TRAILER PLUG TESTERS

I have had on and off trouble with the truck trailer connection, getting a "trailer disconnected" message even though lights, brakes etc work. Airstream says Ford brake controllers are too finicky. Ford says they tested their plug and it must be the trailer. Both truck and trailer have been checked for a good ground. (Google says Ford trailer brake controllers ARE finicky.)

Multiple cleanings of the plugs and lashing the plug in place with a pull tie seems to have solved the problem for now but I thought I might add a plug tester to the mix.

I see two levels of 7 pin testers. One is the $8-10 variety, the other jumps to $25-30. It sounds like both test not only the lights etc, but the brake controller. But the description on the more expensive models seem to be more specific about testing the brake controller.

I don't want to spend a fortune on a tester that I will only use once in a while but, I want to be sure that I am testing all of the most important functions especially brakes. Apparently these testers test the truck plug only thus, if the truck is OK, "it must be the trailer."

What are your thoughts about whether these testers are worth a dang and, if they are, is the difference between the two price levels based on better function or playing to the notion that more expensive is better.
  • First thing I would look at are the female connectors and make sure they are touching each other. By that I mean to themselves NOT each other! If they do not make good contact to the trucks male pins this will give you the issue you are seeing.

    Had the same thing on my Ram, the Rv dealer was pointing his finger at the truck but when I bent each of the trailer connectors the problem went away. Not saying the truck is not the issue but I would try and bend both sides of each of the tabs and see if the problem goes away. If it doesn't then have Ford replace the plug on the truck.

    Hope this helps Don
  • I made my own with 10 Ohm "dummy loads" for the individual circuits and LED indicators for each circuit.
  • therink wrote:
    I simply use a voltage meter at the 7 pin connection to check voltage on each circuit/pin. You just have to know which pin is for each circuit and ground.


    The only problem I see with testing voltage is that sometime the meter will read voltage, but it goes away when there is a load due to a poor connection.
  • I simply use a voltage meter at the 7 pin connection to check voltage on each circuit/pin. You just have to know which pin is for each circuit and ground.
  • Dont know about testers but my Ford would occasionally say there was a fault and my GMC has never done that with the same trailer.