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aire-flo gas furnace not reaching target temp, i have flash code

jtn3833 Member Posts: 1
hello - i'm having problems with an older aire-flo gas furnace.

i set the thermostat to 67 in the morning and it will kick on at the right time (timer thermostat) but won't heat all the way to 67. it will heat to about 62 or 65 and shut off.

it seems to do this throughout the day, getting close to the target temp but rarely reaching it. the temp will usually fall to around 60, then it will turn on again for a little while, repeating the cycle.

a heating/cooling tech told me about the flashing light codes. mine indicates 6 + 4: lockout*, last event open limit or roll-out switching during run.

he said it had something to do with obstructed airflow. i've changed the filter (which was filthy) and opened all the vents but i'm still having the same problem.

luckily it never seems to get below 60.

any suggestions would be very helpful,




  • Spence
    Spence Member Posts: 316
    Flash Code

    You have presented two distinct issues: open limit and roll-out switch. Regarding the limit, if the filter was formerly plugged and the limit continues to open, the blower assembly or the indoor coil (if you have air conditioning) may be full of dirt, or you could have a duct system issue. The roll-out has a very specific job to do, as it's name suggests, which could be related to gas pressure or lack of combustion air.
  • Tim McElwain
    Tim McElwain Member Posts: 4,628
    What is the make and model number

    of the electronic control board? Does the unit have a fixed high limit? What is its maximum temperature rating? The fact that you had restricted air flow (plugged filter) would cause you to cycle on high limit. Replacing the filter and reducing resistance to air flow should solve the problem. Does the thermostat have a mercury bulb? If so it could be out of level which would cause issues such as you are having. The thermostat could also be out of calibration, a professional should be able to calibrate it. Did the heating/cooling tech you refer to actually look at your system? If not you may want them to come and service the unit as there could be other things wrong.
  • unclejohn
    unclejohn Member Posts: 1,833

    Was limil OR roll out. Roll out would be a manual reset not auto.