I have a new to me 2010 jayco 1207. My hot water heater works. I just don't get any to my sink.I have all the shut off valve where they should be but it seems like no water is getting in the water heater. Cold water works fine. If I open the middle shut off valve I get water coming out the hot water side at the sink but of course it isn't hot because it is mixed with cold water. The dealer said to open the relief valve at the water heater but I get water for about 5 seconds them nothing. Any ideas?