Just for clarity, are you meaning while it is blowing just cold air or right after it kicks the main limit switch off?

My in-laws have a M1MB090A furnace - a/c that is just driving me crazy. Has given me problems for a while now. At first it was making ignitors bad and finally it stopped doing that. Then it broke down in the summer because the coils got too dirty for the a/c and we cleaned out the whole system. We h...