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It is in Lockout mode. Something has happened to make it go into lockout. It could be an easy fix. Look of cobwebs in the tubing between the proving switch and the draft inducer motor. Look for air restrictions in the chimney flue. Rusty burners (if applicable). Tripped rollout switches. Some times there could be up to 2 roll out switches on the burner and another in the flue and 2 others in between stuff. . Most times it is a dirty flame sensor. Over the summer the flame sensor gets dusty and the sensitivity gets off. The control fails to FEEL the probe and locks out the gas valve. Most times the failure will be defines by the amount of blinks the red light emits. The sub panel has a guide on it that tells what the blinks mean.
Keep in mind all furnaces and circuit boards are not the same. Look on the back of the door to the blower compartment. You should find the list of diagnostic codes. Look up four blinks it should narrow down the problem. Although from the discription you gave it sounds lie the high limit control. When a high limit appears to be acting up it DOES NOT mean that the high limit needs replaced. The high limit just may be doing its job. This means that the furnace is overheating. Check your filters. Are all of your registers open? Is your blower set on the right speed? Is your blower going bad? Is the blower motor capacitor bad? Is your evaporator coil restricted? Just changing a high limit switch does not always solve the original problem!
Your main limit switch is activated. Maybe for good reason. This switch keeps the furnace from overheating. I have the same problem right now and I think my a/c coil may be blocked, limiting air flow through the heat exchanger and the furnace. Does your gas and main circulating fan come on for a few minutes before the switch activates and the light begins blinking?
Check your furnace filter and any return air ducts in your home - see if they are blocked or restricted.
yes you can and it is on the heat exchanger just inside the front panel it is about 1and1/2 by 2 inches with two wires connecting to it, it has two screws holding it in place, it looks like it is a peice of flat plastic
In the compartment with the blower moter there is a little (button) with two wires going to it.(it is attached to the top (you will have to look up in the compartment) if the unit is installed up and down and not on the side.) (If it is in sidways it is in the section between the two comartments). anyways.... on mine there is a little reset button right between the wires.... press it and see if it makes a click sound. try your start up procedure and see if the problem goes away... I don't know if MY equipment got too hot or if the switch is failing... but it worked for me.