Need some more info,
When the electricity comes on, is this the 120 VAC shore line cord plugged into the power post?
You turned the 12 volt battery on?
Since you said the AC goes out, I'm assuming you mean the air conditioner, and if so then this means 120 VAC. But then you you said the TV's are fine, meaning Tow Vehicle like the truck or TV like television?
What year/model camper? The lights inside are normally 12 volts DC and if you are loosing 12 VDC the lights will dim and the air conditioner will stop if the 12 volt system voltage is low as the control board runs off of 12 volts DC even though the compressor runs on 120 VAC.
And in this case the television which is normally only 120 VAC will still be fine.
If I put the pieces together right this "sounds" like your power converter is going or your battery has a real bad short in it pulling the the converter down.
If you have a volt meter, put it on the battery and see what voltage it is? If it is below 12.0 volts your battery is very low in charge. If it is below 11.5 volts is it close to dead.
The newer power converters will run with no battery while the older ones need it as a big capacitor to stabilize the system. If you unhook the battery and the lights come back to full bright, there is an issue in the battery. If the lights do not change at all it could be convertor needs a battery or the converter is starting to go or is bad.
This sounds like a battery or power converter problem or both
Hope this helps
PS. Welcome to Sunline Owners Club!!!
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
Google Custom Search For Sunline Owners Club