Furnace short cycle & limit switch tripping

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Joined: Thu Oct 30, 2014 12:45 pm

Nordyne MGBB-070ABFC-01

I just recently lit the pilot light since winter is starting up. I was testing the furnace to make sure that it was functioning properly. I set the heat a the thermostat and the furnace kicked on. After a few seconds the blower turned on. I noticed that the unit would run for about 30 secs to a minute then shot off. Then after about 20 secs, it would do the same thing. I started doing some research and it seems it could be a number of things. So I chose the simplest option first. I cleaned the air filters. They where a little dirty. It still seemed that it was cycling. I then opened up the evaporator coil enclosure to clean it up a bit. I had previously cleaned it this summer, but being that the space is tight, it was hard to clean. It didn't look that bad (granted I am not a HVAC guy). After cleaning and looking at all that, it seemed to be running for longer periods.

Now the limit switch keeps tripping after a while of use. When this occurs, the unit will not engage. I have to hit the little switch on top and it turns on. I also notice when I pull the front grate of the get to the furnace the area is warm. It just seems strange the the pilot light would produce enough heat for me to feel it. But, I am not a HVAC person, so this may be normal. I am not certain what else to check. Any ideas?
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