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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7708
Experience:  Furnace, A/C and heat pump specialist.
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See your discussion below on your websit - I have the exact

Customer Question

See your discussion below on your websit - I have the exact same problem - The igniter lights the burners - they go for about 8 seconds then on again over and over - then the Limiter opens - turns off flame and on goes the blower for about 2 minutes then repeats.
"I have a Bryant 394gaw furnace and my burner turns off as soon"
Submitted: 13 days ago.
Category: HVAC
Customer: replied 13 days ago.
I have a 394GAW furnace. Igniter lights burners they go for 8 secnds then off then on again for 8 seconds then off this continues until heat limit opens then flame goes out and blower goes on for a few minutes - probably until heat limit closes - then igniter starts all over again.
Customer: replied 13 days ago.
The 394GAW does not have a flame sensor. for some reason the flame is not staying lit - and the furnace blower is not kicking in - until after heat limit opens.
Expert:  airheatman replied 12 days ago.

Do you have a standing pilot or electronic ignition? Bryant used both. Also give me model on gas valve

Expert:  airheatman replied 12 days ago.

Bryant used both White Rodgers 36E valves or Honeywell VR800A or 8200H valves

Customer: replied 12 days ago.
I have a pilot but it is not on all the time. There is a small igniter that lights the pilot. After a while the pilot fires up the burners in the furnace. The burner will flame for a wihile then go out - but the pilot stays lit. The burners fire up again - over a over and the burners will stay on loger and longer each time. Actually I think this is normal. But in most cases the 3" furnace limit switch will open then the burners go out then the fan will goes on for about 5 minutes - until the limit switch cloases and blower fan goes out. I think the fan going on is merely the safety feature to cool down the furnace. Occaisionally the limit switch will not open and the blower fan goes on just fine. Basically, it appears the limit switch will open before the blower motor starts. I guess the key is I need the blower fan to kick on earlier - before the limit switch opens. Does that make sense?out and the
Expert:  airheatman replied 12 days ago.

Blower should be energized 75 seconds after burners ignite every time.I not we probably have a failing PCB (Printed circuit board). If you have a meter, allow burners to light and check between terminals COM and LO on PCB where fan wires connect.75 seconds after ignition we should get 120vac.

Customer: replied 12 days ago.
I think we may be on to something. I changed the PCB and the furnace is working - however, I still have the same problem with the furnace firing then going out then firing again - initially the period is short - maybe 6 seconds - but then gets longer - until eventually the blower kicks in in about 200 seconds. Then the blower is fine - but the furnace flame going on and off with the blower running. I think I need to check to issues: why is the furnace blower taking so long to kick on and why does the furnace flame cycle on and off? I suspect that the reason it takes so long for the blower to kick on is because the furnace fire cycles on on and off.
Expert:  airheatman replied 11 days ago.

Just to make sure thermostat is not issue,Go to furnace and connect the R and W terminals on board and see if it will stay on.Also if thermostat uses batteries, replace them

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