I will be going on a trip in a few weeks and will be renting a UHaul trailer. I would like to check to make sure the trailer plug is working correctly, before the day of.

I have a volt meter and know how to use it. I just need to know what pin does what. My truck has both the round 9 pin and the flat 4 pin

 

If your renting a U-Haul you will most likely be using the 4 pin...which has left turn, right turn, stop and running lights...set your meter to 12VDC and turn one of the above mentioned functions on...go back to the 4 pin and find a good un-painted ground on the truck ...ground the meters black lead to it and probe the 4 pin with the red till you have 12VDC...it would be better with a test light...but the meter will work.

 

Or find a buddy with a trailer that is in good working order and hook up your electrical to that to test. Simple.

 

yup.. that would work too.

 

I picked one of these up at a discount shop for under $5. Super simple, uses LED's to show continuity. They also sell em at Harbor Freight, I think. Small, so you can keep it in the glove box just in case.

 

Perfect