My limit switch come on then go off over and over.

The unit is probably overheating. Start by checking the air filter.

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Originally Posted by KC13

The unit is probably overheating. Start by checking the air filter.

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I already check the filter its clean and the vent stack is clear of debris

Does the blower run?

Yes the blower run good

Is anything blocking or restricting the supply and/or return registers?

No the return is close to the ceiling. Can the coil be restricting enough to over heat the unit. I did not check that or could just be the limit switch.

An airflow restriction of some type is more likely. If the indoor coil is clogged with dirt, your air filtration is probably insufficient.

It could also be a weak or out of range limit switch if all else checks out. You might also check the gas pressure and make sure it is as listed on the furnace label. A furnace that is overfired can also cause this problem.

Thank you I will check the coil if that check out I will check the gas pressure. I just want to be sure before I get a new limit switch and have the same problem

Smart move. Many folks just run out and buy a part and think the problem is solved and that in many cases is not the way it works.