Originally Posted by bobgails1942
snip....Is the dealer correct?
Welcome to JOF !
No....., as mentioned it's either source separately, or both at the same time.
It appears that you are still under warranty, I would take your TT to the RV dealership for warranty service if you don't see an easy fix (breaker, etc.). If your RV dealer still holds to the belief both sources (110V/LP) have to be on at the same time for HWH operation, have them re-read your Jayco owners manual.