Hello

My gas home heating system turns of suddenly and the desired temperature has not been reached. This started happening 2 days ago.

When we go to bed we lower the temperature to 58 degrees and when we are up in the morning we raise the temperature to 68 degrees. Yesterday morning I raised the temperature to 68 degrees and the heat kicked off as expected but turned off unexpectedly at 62 degrees.
I then jiggled the thermostat by turning it down to 50 and back up to 68 degrees and it kicked off and worked good all day. This morning the same thing happened. And I again juggled the thermostat by turning it down to 50 degrees and back up to 68 degrees and it came on again. We have one of those old circular mercury thermostat.

Can you tell me what you think may be the problem.

Thanks
Wayne

Hi Wayne. I think you have answered your own question. Sounds like the T-stat is bad(Could be the anticipator is bad in the stat). This would explain the temp swings. You can get a decent replacement at home centers(Depot, Etc.) for around $40.00. The Honeywell Round T-stat is a good choice and widely available. They are easy to install. Just take your time and follow the instructions, especially turning off the furnace power before you start. There are only 4 wires that need to be hooked up... Good Luck...

Before I bought a new thermostat, I would check the furnace and wiring. Shut the power off, and pull the thermostat loose. Remove the red and white wires and connect them directly. When you turn the power on, the furnace should start a heat cycle and stay on as long as the wires are connected.

If the furnace shuts off before the house warms up, the problem is in the furnace or wiring. The furnace has a sensor that shuts the furnace off if it overheats. It could be going bad and shutting the furnace off when operating normally.

If the furnace runs normally until the house reaches the temperature you want, disconnect the red and white wire. You have a start on changing the thermostat.

Yeah, let us know how it turns out...