Have a 19 yr old HEIL furnace, model # GNJ075M12A1, that was working until yesterday. Now the inducer motorvent is the only thing that runs on it, and it doesn't stop unless the power is cut off. Have tried resetting it through both power cycling and thermostat cycling it (pulling batteries and also lowering heat and back up for fresh call), have tried jumpering vacuum switch as well as sucking on the hose to close the switch to no avail. Have checked the transformer near the circuit controller board for voltage, and it shows 26-27V coming from it. There is no voltage going to the vacuum switch, but I think that might be by design. It has a Honeywell smartvalve in it, and I know the logic on it will cause certain things to fire at the right times. This smartvalve was just replaced 2 months ago, so it's probably not that. Not sure what else to check. Could a bad ignitor cause nothing to happen like this? Thanks