My upstairs thermostat shows the little flame in the lower right-hand corner, but the heat doesn't come on. I have it programmed to go to 73 degrees and it was on 70 for a while and went down to 67 overnight. My downstairs thermostat works fine, so I am not sure what is wrong with the one upstairs.

if there is no control of air movement between floors and you have it on cooling then any cold air will go down to the lower floor
or alternately if you have it set on heating all the hot air will rise to the upper floor
where is the system located (upstairs or down stairs ) and where is the thermostat located
to get control close any upstairs to down stairs doors or erect a heavy curtain across the stair well

If you are talking about the difference between heating mode and cooling mode and the room setpoint, you can not change it. It comes from the factory with a 3 degree difference. In other words if you raise the heat setpoint until it is within 3 degrees of the cooling setpoint, for every degree you raise the heat setpoint the cooling will raise a degree.
About all you can do is increase the distance between the heat and cooling setpoint. To do this either lower the cooling setpoint to 3 degrees higher than the heat setpoint you want and then increase the cooling setpoint the desired setting. For example heat and cool setpoints are 67 and 70 respectively, and you want 65 and 73. Lower the cooling setpoint to 68 and then raise the cooling setpoint to 73. Now your heating will come on 3 degress lower than 68, the 65 you wanted and cooling will come on at 73. Remember, the thermostat new setpoints will turn on the cooling at 75 and turn back off at 73 and heat will turn on at 63 and turn off at 65.
You can perform the same using the heating setpoint, just have to look at it backwards. If you need to lower the difference I recommend a 8000 series thermostat. They are the most functional thermostat that Honeywell makes, be in mind they are about 3 times more expensive and many of the setting require a well trained tech to interpret and set properly.
Hope this helps.

You never said what type and model of thermostat you have....... If you have a digital stat You may have to lower the HEAT setting below 67 degrees if you want to set the AC to 70 degrees. If the thermostat has an Auto feature then it has to have a 3 degree differences between heating and cooling. On the newer models it does it automatically if you lower the Cooling setting it will lower the heating setting......It this doesn't help repost with more information so I can help you better....

The thermostat is calling for heat, and the battery icon means that the batteries are low and should be replaced. If the thermostat is wired to run on battery power alone, replacing the batteries usually corrects this problem. Hope this helps! Jim

If the dryer is running then the thermal fuse is okay.

The temperature is controlled by three parts. There is the operating thermostat which is on the blower housing and is rated at 150 degrees. This is high heat.

The operating thermostat sits in a thermostat heater which is controlled by the temperature switch. The temperature switch controls how much voltage passes it to the thermostat heater. This is how we achieve lower temperatures. There is about a 15/20 degree difference between high heat and low heat.

The restricted vent may have caused the appearance of the dryer running hot.

I would suggest you check the temperature coming out of the exhaust. It can be checked with the vent hose pulled off. Any thermostat with a range between 120 degrees and 160 can be used. With the vent removed check the temperature of the air in the exhaust. At high temperature it should cycle between 135 degrees to approximately 155 degrees. This is high heat.

If you turn the temperature switch to a lower setting such as delicate you should see a lower temperature in the exhaust. It may only be 15 degrees lower but it should show a lower temperature.

I hope this information helps to resolve this problem.

Hello,lPlease check zone valve at boiler.

It's not your thermostat. Go to where your heating system is and give us a make and model number so we may help you.

Sound like there are running on emergency heat which is elrctric.Have the system checked out buy a local heating and cooling company. Have they checked the filter and changed them.

problem is not the thermostat, thermostat is an on-off switch that happens to work on temperature. Your furnace is locking out. cycling the heat off switch resets the micro-processor in the furnace. You need to diagnose the problem in the furnace, to go further we will need the model and approximate age of the unit

sometimes the furnace does a better job than anticipated, i wouldn't worry about it, especially if the furnace shuts off.
the setpoint is the temperature you want it to be
cycle lenghts are determined by how much recovery you are requesting. for instance, in the morning when you wake up, you want the temperature to be at its setpoint. what the thermostat will do is make the furnace run a limited lengths during the recovery process.