Yesterday we had a problem with our Heil DC90 Furnace. The fan is working but there is no heat. The Furnace has one of those Honeywell Valves on it and I think it is malfunctioning. I tried to shut off the valve and turn it back on and this worked for a little bit last night but by this morning the valve would not allow the pilot lite to come on. Is there anything I can do to trouble shoot this?? I was told by a repair guy that with the valve tripping out the Heater Exchangers may need replacing or we need a whole new furnace. I think they just need to replace the Honeywell valve box the furnace would run fine. Any thoughts?