My winegard booster with green light is supposed to be OFF if
I'm using the outside cable hookup.
Also there might not be any splitter because the winegard wall
plate boosters have a built in splitter.
IE. the antenna comes to the back of the booster, you get an outlet on the
booster and there is also a connection on the back of the booster
for a cable input AND for a remote outlet to another TV somewhere
If all these are connected, be sure the booster is off when you try
the outside cable hookup. If this does not solve your problem
I'd follow others advice and run a temporary wire directly from
the back of the booster to the bedroom TV and make sure it
works that way.
Then try removing all the end fittings (if they are removable)
and check to be sure the installer didn't botch one of the
cable ends. I found they had cut off the shield in 2 places in
my previous trailer. We had lousy reception. When I cut
and properly installed the connectors WITH the shields in tact, our
TV improved significantly.
AND it's always possible they stuck a screw thru your cable that
runs to the bedroom