I have the DGAA077BDTB model which will only start if I turn it off, then back on. Then the furnace will power on, and the air will blow but it's cold. Then it will stop after 5 minutes or so and won't go back on. It's flashing 4 times which means "limit switch open" but I have no idea what that means. My furnace has not been used for months and worked fine last time it was used. If anyone can help that would be great.
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