RV Repair: Running, brake, stops lights inop, cable head, battery charger

Question
When I hook up to my vehicle none of my lights. turn signals brakes work.  I have used a meter and see all the correct voltages at the cable head on the van.  I have checked at the cable head of the camper and see resistance where I should see for the lights.  I physicallt added a ground wire from the vehicle to the camper to no avail.  I also physiclly jumped a wire from the vehicle to the camper with no results.  I am at a total loss.  The camper is about 7 years old.  HELP!!!!

Answer
I am sure you checked for corrosion.  try a battery charger set for 10amps or so.  You would put a probe in the battery charger clamps and touch the black to the ground.  touch the red to the connectors one by one and see if the lights and brakes come on correctly.  If so, there is a problem at the connection of the van to the camper.  

good luck.  sorry so long with response.  I was camping the last two weeks and forgot to turn off the all experts questions.