I had a problem with the front heater in my 99 dolphin 5370. I thought it may have been the control board. I took the two control boards out of both front and rear furnaces and switched them. The rear still worked fine but the front stayed the same. I put them back to the original configuration and the problem persisted. That showed me the problem was not with the board.
You might try switching yours and see what happens.
I then undid all the connections, cleaned them with electrical contact cleaner and reconnected. I used a pair of needle nose pliers to gently compress the connections and Viola!!! The front started working!!
Apparantly there was a weak or dirty connection somewhere. I STRONGLY suggest you take a digital close up of all the wires and connections prior to undoing anything. There a number of wires and plugs. A color picture will save a lot of headaches (
) when hooking everything back together.
Good Luck and Happy Trails!! -- Kevin