On our Sightseer, I climbed up to where the cable goes into the cap in back- where there is a small rubber grommet. I took off the grommet and began pulling out all the slack in the cable which was doubled back and forth and then tightly bound with a plastc ty-rap. I cut off the ty-rap and fed all the slack gently back into the hole. Then I tested the camera and it worked...this was over a year ago and it's been good since.
You didn't say what type of view screen it is.
If it is a Jensen model and there is a reset button,
push it and that may fix the problem.
That's how I fixed mine.
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2010 Coachmen Freelander 30QB E450 V10
Have Kids Will Travel