Carrier Unit, Heat works....sometimes

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Carrier Unit, Heat works....sometimes

Postby Freelandm » Wed Dec 14, 2011 3:57 pm

So I have a question for you all. I will try to explain this as best as possible in the short 2 days i've been in my attic trying to figure out the problem. I have a Carrier unit installed around 2004. I apologize I do not have the serial/model #. So this winter I noticed that my heat would randomly work. The thermostat works fine. I could hear the unit kicking on and attempting to turn on for about 1-2 min than it
would shut down. This cycle would have happen about 3-4 times and then nothing. So I went up into the attic and after being up there for about 40 min I noticed this. There are 5 burners, when the unit attempts to work, the 2 top burners come on. The other 3 burners wont light and then the unit shuts down and attempts the entire cycle again. The flame sensor is on the bottom burner. The amber light gives me error code 34. I've reset the power to unit and it tends to work for a little bit then the same thing happens. Thanks for any help. If there are any questions, i'll try to respond asap.
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- Carrier Unit, Heat works....sometimes

Postby 4ftBanger » Wed Dec 14, 2011 6:37 pm

Your furnace is having an issue with gas delivery to the main burners. When the sequence starts the draft motor should run for about a half minute, then the ignitor should begin to glow, followed by an audible click from the gas valve right before the burners light. If all 5 burners do not light together (or in very rapid succession) then gas is being deliverd too slowly through the manifold piping. Based on the information that it does not happen every time I would probably rule out dirt or restriction in one or more of the burner orifices. I'd suspect that the gas valve itself may be failing. If the electronic solenoid doesn't reach full open position immediately then it is probably getting stuck part way open. This can be caused when the gas pressure is too high or too low, or it could be a mechanical issue with the gas valve itself.
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