Burner flame not hot enough

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Hi I am new to this site I live in Detroit mi and I have been doing hvac for 5 years.Any way I have a problem I just cant figure out An colman evcon furnace nat.gas model dgato56bdd ser number 951244522 the call was no heat found power 24 volts to gas valve but valve was stuck closed so I replaced the valve.started the furnace only to find the heat exchanger was not getting hot enough checked gas pressure found it was good 3.5 in water.so I replaced the fan limit and high limit.

Thinking because all else was good flame sensor and igniter was good and clean and every thing had proper voltage but I was wrong!I can touch the heat exchanger right before the blower comes on temp out of nearest supply is only 50 f I also in stalled a new non program t-sat and it works properly please any info would be great.

William

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Was this a sudden problem or an ongoing one ? Make sure orifices, burner tube is clear and burner has strong flame.

Thanks,
Robert

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Robert thanks for the info and you were right found spider wed inside of orifice.Cant belive I over look that thanks again.

William