Let's start with the easy part first; all the heat exchangers in the Hurricane system and the Seaward hot water tank are dual-wall which means it is safe to use regular antifreeze since there is no chance of contamination of potable water. You do not want to use pink RV antifreeze in the system; that would be a disaster since it is not meant for high temperature heat transfer. One could use extended life engine coolant, which is red, but that would be an unnecessary cost.
There are red "boiler fluids" which are non-toxic and can be used with single wall heat exchangers. There was a thread on this forum a few months ago in which these were discussed. However, there is no real need for them since all the heat exchangers in the Hurricane system in your coach are dual wall.
As for the fault in your system, the user guide states that this fault indicates a short in the pump which you probably already know. If the the pump is working but the board is indicating an error condition, I guess it could be a board-level problem. My suggestion is to call Kevin Lambert at ITR; he is great at helping owners like us pinpoint problems. He can be reached at: 360-993-4877 in Vancouver WA
