My house was cold one day. Looked at furnace filter and seen the flames go out but furnace was still running then the igniter glows a few seconds later and it reignites. I get no code or flashing lights had furnace guy come and clean flsme sensor which didng fix it. What could it be? On another note i thought the flames were going on and off alot until i watched it for a while but i hear and feel thumps from the furnace while it runs i thought it was flames is that normal its not the ducts its the furnace thumping
Goodman gmh furnace flame cycling while running
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A few things can cause this.
Rule out the thermostat by turning it to off, then place a jumper between terminals R and W on the control board.
Let it run for a good 20-30 minutes, monitoring operation. This furnace should start on low fire and after up to 12 minutes cycle to high, but it may be set up to run on high all the time. (factory default)
Check for a fault code as soon as the burners cycle off during a call for heat.
It could be a pressure switch dropping out when it shouldn't. (may not be that the switch is bad - ie if the draft produced by the ventor motor is marginal)
Make sure the condensate lines are clear. Check exhaust/intake pipes for snow buildup.
To see what's going on, you may need to check for voltage drop across the safety devices while its running. Also possibly flame current, so if you don't have a meter, get one that can check dc micro-amps. The meter is a must-have for diy repairing anything electronic/electrical in nature.
Rule out the thermostat by turning it to off, then place a jumper between terminals R and W on the control board.
Let it run for a good 20-30 minutes, monitoring operation. This furnace should start on low fire and after up to 12 minutes cycle to high, but it may be set up to run on high all the time. (factory default)
Check for a fault code as soon as the burners cycle off during a call for heat.
It could be a pressure switch dropping out when it shouldn't. (may not be that the switch is bad - ie if the draft produced by the ventor motor is marginal)
Make sure the condensate lines are clear. Check exhaust/intake pipes for snow buildup.
To see what's going on, you may need to check for voltage drop across the safety devices while its running. Also possibly flame current, so if you don't have a meter, get one that can check dc micro-amps. The meter is a must-have for diy repairing anything electronic/electrical in nature.
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did he pull the flame sensor check it to be sure its good....still could be bad ..had one last week concord furnace ,,,,cleaned it reinstalled it same problem flame dropping off...replaced it ...furnace still running good....
Just jumped the red and white wire furnace was starting up just as blower motor was starting up the flames went out with everything still going the starter started gloeing again and flames for another 5 sec then out again its completly random tho some times it only happens once while heating. The whole time the flame is cycling on and off the furnace is still running. No codes at all. And would the furnace still run after the flame sensor triped from what i see online the whole furnace shuts off. And randomly i hear thumps and like the fans slow for a split sec or somthing like somethings kicking on and off.
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Measure the flame sensor current in micro-amps is you have a meter and wires with alligator clips.
It's done in series with the sensor, dc micro-amps.
Does the inducer/ventor continue running when this happens?
if yes check the pressure switches for voltage drop. ov = closed, 24vac = open
It's done in series with the sensor, dc micro-amps.
Does the inducer/ventor continue running when this happens?
if yes check the pressure switches for voltage drop. ov = closed, 24vac = open
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17,806 Posts
safety opening first, gas valve closing in response. got to check all the safeties.
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