Mine works fine too with the 9 to 4 adapter plugged in with a utility trailer and a cargo trailer. I did have an adapter one time that didn't seat well into the plug on another truck. Tried another adapter and it worked fine...the old meter helps...I had a bad ground on a trailer once that acted like that (running lights ok, but no signal or brake lights).You're gonna have to get the old meter out and see if there's applicable power coming out of the correct pins for the lights. I gotta say mine work fine on my 9 to 4 pin adapter for my utility trailer. 18months now for me.