Gas and Oil Home Heating Furnaces - Gas furnace Ignition lock-out

I have a Trane XE70 furnace TUS0808936A0 with electronic ignition (White-Rodgers / Emerson Electric model 50E47-60). Some of the electric wiring was being updated in the home which was built in 1955. Inadvertently, the hot and neutral wires were switched on the line supplying the furnace. Later that day after power was restored the switch was noticed and corrected. Now, the gas furnace will not heat although the blower will work in the 'on' setting. In the furnace there is a sticker stating that the furnace ignition in polarity sensitive and will lock-out if not connected properly. How does one reset the ignition module or remove the lock-out so heat can be restored?

Shuting off the power to the furnace should clear the lockout. I would leave it off for 5 minutes or so. Sometimes it doesn't take as long. Once you turn the power back on and it calls for heat it should fire.

If it don't work after you reset the power, the ignitor may of gotten fried..

Do you have a Green or Red LED light on the control? Does it flash anything?

The W-R/Emerson ignition control has a red LED in the lower left corner of the unit with the following sticker: "If red light stays on, replace control. For flashing light, refer to service instructions".

My light is dark (not on) even though power from the 24v transformer is present. Is this normal?

Try to trace back to make sure the wire has not come undone from the transfromer to the ignitor. (some model needs power from the transfromer, not the t-stat)