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Bryant Gas Furnace - blower sarts and stops

6K views 7 replies 4 participants last post by  Tator1076 
#1 ·
We have a Bryant gas furnace (model 394GAD I think). When the thermostat calls for heat, the burners start up, then after 45 seconds or so, the main blower. After about 3 minute, the blower stops, but the burners remain on. Then 30 seconds or so later, the blower starts up again. Three minutes or so later, blower stops, burners continue, then after 30 seconds, blower starts up again. Keeps repeating this cycle until temperature on thermostat reached - then whole furnace shuts off (blower and burners). Any ideas?
 
#3 ·
Furnace has been in place for 18 years - worked fine until about 2 months ago. Changed out thermostat to see if that helped - it didn't. There doesn't seem to be any thermal limit switch that determines if main burners are hot enough before starting blower - just a time delay circuit - although, I agree, the system is acting as if there is one.
 
#5 ·
Timer circuit is located on the main control board. It is apparently solid state (according to the circuit diagram). I have ordered a replacement board and will try that. However, I was wondering if there really is an "air low temperature" limit in this furnace or not.
 
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