I have a gas burning heater which uses Millivolt heat-only thermostat. The old mercury thermostat that came with the Southern Burner heater failed due to rust and I replaced with a Honeywell unit which after one year stopped working just now. It has some rust and the contact is faulty - if you jiggle the coil it starts up. The magnet part looks OK. Is there a reliable waterproof unit out there? Thanks.