Heating, Air Conditioning, Fridge, HVAC/Thermal Zone gas furnace


I have a Thermal Zone heating gas unit. It just started this issue. When the thermostat tells it to kick on and supply heat this is what happens. The fan starts. About thirty seconds later the igniter starts to glow. About thirty seconds later the gas kicks on and the burners light. In about thirty seconds there will be a click, the burner will go off, and then the fan/blower will start up. Result - no warm air but the blower works fine. Any ideas? This does not happen every time but enough to be problematic because if the burners are not running it will keep cycling.

When working properly and the tharmostat calls for heat first the vent exhaust blower starts and runs, next the igniter glowes, next the burner lights, the blower is on a delayed switch and comes on about a minute after the thermostat calls for heat and will stay on untill the thermostat is satasfied even though the burner shut off prematurly, the blower turns off on a delayed switch also.
When the burner dose light the flame burns on a flame sensor and heats the sensor which keeps the burner on untill the thermostat is satasfiedh.
You need to gently clean the flame sensor eliment with a fine piece of sand paper or emery cloth.  

Heating, Air Conditioning, Fridge, HVAC

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Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

Hands on since 1950

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