4 Red Flashes on York Furnace / Humidifier not working


Old 11-25-14, 05:08 PM
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4 Red Flashes on York Furnace / Humidifier not working

Hi All,

I've got a York Furnace (YP9C080C16MP12CA) and an Apriaire 550 Humidifier. The humidifier is not currently working (solenoid does't open to allow water to flow out) because 24V power it not going to it. When I look at the controlboard under the furnance, there is an LED that flashes red 4 times which indicates that it could be: "High limit switch open or defective temperature sensor or 24 volt fuse is open. This may be caused by a dirty air filter, improperly sized duct, faulty blower motor, restricted circulating airflow an open fuse on the control board"

Can anyone interperate that to tell me what to do next? Does it mean that my transformer is bad and I need a new one?

Thanks in advance!
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Old 11-25-14, 05:38 PM
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Welcome to the forum!! A 4-flash code is most often caused by an air flow restriction often due to a dirty/clogged air filter or a dirty a/c coil (if installed). Also, make sure all air registers are open, the return air ducts are not blocked by furniture or other objects. I suggest you re-set the control board by turning off the power and then back on and then set the furnace to heat. With the access door removed and the door safety switch pushed in watch the sequence of operation to see at what point the control board throws the flash code. After calling for heat the sequence of operation should be: inducer starts up, pressure switch closes, ignitor glows, gas valve opens, burners light, blower comes on and furnace continues to operate until set temperature is reached at thermostat.
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