If this is a 120 volt unit, the control is 24 volt, powered by a transformer mounted in the back just under the main fan. A bad transformer could give the symptoms described. To check this, have a meter on the thermostat wires when the unit is working. the white wires ae the thermo wires. Find one that reads 24 volt AC against the can of the furnace. see if the 24 volt shuts off when the furnace fails. If so, change the transformer.