I have a Tempstar gas furnace with White Rodgers hot surface controller. After call for heat, controller indicates all OK (green led on), draft blower comes on, igniter glows, gas is turned on and the burner ignites. The temp sensor (recently replaced) glows red and the burner stays on while the limit switch indicates the heat exchanger warms up. As soon as the main blower is turned on by the limit switch (or as long as about 5 seconds after), the burner (along with the draft blower and the controller) shut down. The blower continues to run until the limit switch cools and then the cycle repeats. Help. Thanks.

The main blower should not be controlled by the limit switch since that switch is only supposed to turn off the furnace if there is a problem. The blower on the gas furnace is controlled by a fan switch. Sometimes the fan and limit switch are together in one housing.
I believe your fan switch is defective or out of calibration. Usually best to replace it if that is the problem.