Jensen TV issue

  New guy to forum here so just shoot me - or better yet, redirect me if this has been covered.  I've got a 6 mo old 12v Jensen 32" tv installed in my RV (2006 Thor class c).  I used the old TV 12v line that was up in the cabover for power but the original TV was 120v.  Here's the issue: when I'm on shore power the TV works fine.  However, when I go only on battery power the TV will run about 2-4 minutes and then shuts down.  I've tried two different coach batteries - both fully charged - so not a battery issue.  I do have the stereo and the winegard sensarpro also on the 12v power line in the cabover.  12v power line in cabover is about 14 or 16 gauge.  BTW, stereo works just fine when on battery power.  My thoughts: I've heard the Jensen TVs can be voltage/power sensitive so ...  While I measure 12v at the TV plug maybe (???) I'm getting a voltage drop when loaded with the TV on the relatively small 12v line that runs to the cabover that's just enough to not support the TV when on battery but with the boost of the converter it works.  BTW, measured 12v at plug with both battery and then converter on.  Note: my voltmeter is meant for higher voltages so no tenths.  I'm going to try a direct connect to a battery (when the temps here in STL rise above 15!!) and see if the TV will work when I bypass the long wiring run from 12v panel in back of RV to front.  Anyone run into an issue like this with a Jensen TV? BTW, I'm dreading snaking a heavier 12v line from back of RV to cabover!! 

OK, no replies so far but I'll keep the post updated in case someone else runs into this issue.  Anyway, found that the 12v line to the tv/stereo was also the same line as the CO2/propane detectors were on.  That line went into a low current fuse location.  I moved the line over to a spare 'full current' fuse location.  Turned on TV and thought I had it!  But no, after about 5 minutes the TV went into it's same old shut down mode.  So I drug a spare battery into the coach and wired the TV direct to it.  No problems.  Ran fine.  So that tells me I've got a voltage drop issue on that small 12v line up into the cabover.  However, I did find in my electrical junk a wire with a lighter plug at one end and the same 12v barrel plug on the other that fits the TV perfectly.  I can plug the TV into the vehicle battery via a lighter plug in the dash.  Did that and tv runs perfectly.  Yeah, gotta be careful to not run the starter battery down but when underway this won't be an issue.  Long run, it looks like I need to run a better 12v line into the cabover.  One other thing I might try is a small voltage regulator on the existing line (remember, the tv/stereo does work when I'm on shore power and the converter is 'juicing' that 12v line).  I'll let you know if that works!

You have identified the problem.  You have a voltage drop due to wiring that it too small.  Run heavier gauge wire or move the TV closer to the battery source.  I would run heavier wire.