Does the ignitor come on? Two usual culprits are the split coils, the solinoids Kenmore81 mentions on the gas valve in the front. Many times, it is simply the thermal fuse on the back by the main operating thermostat by the blower housing. It is the white strip with two wire terminals. EVEN if you read continuity over this fuse, it can be bad. It is redundant, buggy and unnecessary. Clip, Clip, Strip, Strip, nut wire. matt