We were having a problem with our 2001 Marquis Destiny Coastal Series heating up and after a couple tests we came to the conclusion that we needed a new board. After putting in the new board, it started up fine and the spa was heating up but then a couple different display messages came on. The light was showing that it was heating up but then it said "dr" (no water in the heater). When that code shows up it says to press any button to reset after checking the water level is okay which I did. Then the red light came on showing it was heating again and going thru it cycles. I continued to do that and the water temp went from 59 to 65. Then this morning it shows "LF" which means a low flow problem (not enough water detected in the heater). After talking to a guy at a Marquis store, he said that it sounds like we have something blocking the lines which is what we thought too. So my husband took the unions off to check to see if anything was blocking the lines which he didnt find anything. We already took the filters off too and still same codes show up. My thought is to stick a house down each hole where we screw in the filters and turn it on so the force of the water would push whatever is blocking the line through. Or get rid of any air bulbs if that is the problem since the spa has been empty for 6 months now. Could it be a pressure switch or something? How can I determine for sure what my problem is? I need to know for sure since if I need to buy a part, the spa store I have to go to is 50 miles away. I would really appreciate any help that you can provide concerning this.

Thanks,
Paula