i think the dish may be powered from the lmb feed as that is normally 18v
you sometimes see a dish with a light shining from the lmb to the dish and that is powered by the lmb supply
OK, it may be me, but there has to be a supply to the unit, which then boots it up to 18v since the MH battery voltage is only 12 v nominally.
The LNB is not directly connected to an 18v source independent of the vehicle supply is it ?
That's why my first point to check would be that supply cable, from what you have described, it must go from the vehicle to the control box, be boosted to 18 v and then taken to the box within the signal.
Maybe I am missing something, or being dense, but to me that voltage must come from somewhere connected to the MH battery.
The installation instructions confirm that it is NOT connected via a separate supply, but takes its power from the decoder or the TV wherever the decoder is built in. This, whether it is the freesat box, or the TV will be connected to the 12v MH system.
That must therefore be the point to check, 'cos if the TV is not receiving the power it cannot pass it on. That must be the route unless there is a separate satellite decoder box which would also have a 12v power supply.
These units need to be checked for power. If the TV standby red light does not come on, when it is turned on, the supply to the TV must be suspect. If it does then the connection from the TV to the LNB could be the problem - I do not know what format that takes; many are HDMI connections, others use scary or perhaps just the aerial lead - those connections Ned to be verified if the TV standby light comes on but nothing else happens.
Thinking of ALL the front line staff working to try to help others;Doctors, nurses, paramedics, cleaners, NA's, catering staff, support services and all others. Their work is appreciated more than you can ever realise-keep strong and safe.
Any typo that I make means the errorists win.
Remember Jo Cox and what she stood for.
Any comments above are only MY OPINION
and should be read as that.