We have an older gas wall heater that the thermostat has never really worked... basically "on" or "off". It hasn't been a problem because we don't use the room much. It was working this past winter. We are now selling our house and the inspector said it would not fire. The pilot light is on. Someone told me that it probably did not fire because the room temp was 80 degrees. Is this a possibility? Is there anything we can clean or adjust? I really don't want to have to call a service person. THANK YOU!:)

Yes it is possible. No clean and adjust. You need to find the thermostat circuit and bypass it to see if the unit comes on.