I installed the Trane TR400 in May 2017. We didn’t use it much in 2017, but did use the heater more in 2018. Toward the end of the season (August 2018) we noticed that the LO indicater woud come on and shut the heater off. We were getting the same LO indicater this year, and call a local service tech in to look at it. He said that it was either a dirty filter causing a reduction of pressure or the Polaris being run at the same time. The filter was clean (so that was eliminated), the Polaris is not on the input side of the filter or heater. It is installed after the heater. I am still getting the LO indicater. The LO indcater goes on for a while then the heater goes back on, then after a couple of minutes come back with the LO indicater. The Heater keeps alternating between off (LO) and back on again. What could be the issue?