OK.  While driving home from PA with the new trailer (and truck), we had no left turn signals or left brake lights on the trailer.  I was dumb and didn't think to check the fuses... just assumed the truck had been wired wrong.  We DID have really bright running lights, and working right turn/brake signals.

Tonight I brought the truck back to the place that installed the brake controller, and they replaced the "left trailer turn signal" fuse.  Then they checked out the truck wiring with their machine doohickey that plugs into the truck outlet... it was at that point doing fine.

When we got home, we plugged the trailer into the truck WHILE IT WAS OFF just to be cautious.  When we turned the truck and lights on, the running lights on the trailer were really dim AND when the turn signal was applied the opposite side running lights and turn signals blinked.  That is, with the right turn signal on the truck, the lights all along the entire left side of the trailer (including the running lights) got brighter than they were, and the lights all along the entire right side of the trailer (including the running lights) got dimmer ... maybe even shut off, I dunno, I was up front doing the turn signals.

At this point I don't really even dare haul this to the service center... it's pretty far away.  What sorts of things can we check out here, and how?

Thanks!!!!!

Never mind, we have a bad ground.  The first time we tried it tonight, we just backed up near it and plugged in the electric without hitching up.  That's when everything was berzerk.  When we hitched up, everything was OK.  That means bad ground, hubby says.  It needs to be fixed but it's driveable... which means I can go to my clinic on Thursday. 

I'll leave this topic up just in case it helps someone else, someday.

If you apply some dielectric grease to the male pins in your trailer plug, and then couple the two halves together, the grease will keep the pins from corroding. While ensuring a better electrical contact, the grease will also make the actual coupling an easier affair. This works equally well on new or older plugs.

Gard