My heater for whatever reason will no longer ignite. The ignition does spark and I smell gas so assume the gas valve is opening but no ignition as the blow is only blowing cold. Please help on where i should look next. Below is what I have checked. I have 100ilb propane tank and it is about 1/4 to 1/2 full.
Ignition does spark.
120V to Xformer and 24v from Xformer to Gas Valve on/off switch.
All Tubes are clean and clear of derbies.