Backup camera woes

[admiral1]

2001 Monaco motorhome with RCS70 camera and monitor. I have removed camera and monitor from coach for bench testing because of no picture problem. Bench testing with monitor pluged in to coach power plug and monitor and camera connected with 60ft of new coaxial cable I get no picture,but when I plug short 2 foot pigtail camera to monitor I get a picture. so where is my problem what would cause this,my grounds seem to be good,i have ohmed them to ground, and I have 12.48 input to the monitor. thanks for any help.

[CountryFit]

60 feet may not be a concern. you may clean the contacts of the cable with sandpaper or "deoxit" (can get from radio shack). good luck.