My Chromotherm III jumped to a -AC reading in place of the current temperature today, and the furnace is not turning on. Breaker is on, nothing else has changed (unlike as in txhelp's problem) Right as our outside temp dropped to 31 F. We have a 500 gal propane tank reading 50%, but also our propane fireplace flame, although on, is not responding to the flame height dial. Tank possibly empty (contrary to reading) and causing all this? Mechanic is an unhealthy lead time away. Any suggestions in the meantime?