I have a Coleman Evcon pulse fired gas furnace (yes, Coleman does make a pulse furnace) that is causing me some headaches. The call for heat is there, all limits and the air pressure switch closes......the call goes through the ignition module and the ignitor fires. Gas valve opens and the units runs perfectly. Indoor motor comes on and all is well.
There is no flame sensor!
40 seconds pluse after everything seems well the gas valve kills the flame when there is still a call for heat. limits are still closed and the draft motor is still running. I have replaced the module with a new one but the furnace is doing the same thing. I have not seen anything like this in 20 years of HVAC. Any ideas?