Tell me how to fix furnace lockout.
If you had a series of brown outs, you need to turn the furnace off, let the power dissipate, and turn it back on.
I know brown outs can cause it to shut off if it does not get enough power.
Repeated brown outs from the power grid can cause the furnace to lock out, and the solution is essentially turn it off and rebooting it.
That only fixes it if we’d had brown outs.
The same thing can cause the furnace to lock out if you’re running every appliance in the house, pulling more load than what supports the furnace too. If the furnace control board has errored and locked out, you can hit the start or reset button to try to bring it back up, regardless of the cause.
What if that isn’t enough to get past the lock out?
Turn it off and back on via the power button or turn it off at the breaker.
Now we’re back to reboot it to fix it.
That helps if it is a single error. However, that won’t fix a mechanical problem.
If it is a mechanical problem, then it will run until it fails and locks up again.
So check the air filters. If the filters are so clogged it cannot get enough air, it will start up before shutting back down.
Yes, and repeated on-off cycles cause it to shut off.
Another common cause is carbon and ash on the flame sensor, so it turns on, then off, when it does not recognize the flame is on.
You can get that same error when the thermocouple is too far from the pilot light.
Yes, which is why if you take the thermocouple, pilot tube and flame sensor out that you put them all back in nice and clean before making sure both the sensor and thermocouple are an inch or so from the pilot light.
What else could I do to fix this?
It may be cycling on and off because there is too much humidity in the unit for the flame to ignite or burn hot enough.
I’d be able to tell if that was the case if the flame was orange or the carbon monoxide detector was going off.
It is more obvious when you hear gurgling in the furnace when you turn it on, though changing the filters and emptying the humidifier may fix that.
Any other tips on how to fix it cycling until it locks up?
If it is not a sensor or environmental variable, the control board may have a flipped bit, erroring out.
You’ve already told me to try rebooting it.
And if that does not work, you won’t feel like an idiot when the repair tech tries to reboot it to fix the errors. Or guilty at the price to replace it.
