Thermostat show cool on but not running - Honeywell Programmable Thermostat Heater

O and B are both for your reversing valve. Most thermostats have only one (Orange or Blue) wire instead of both. Because of this there should be a setting to select whether the wire will be powered for heat or powered for cooling. HVAC manufacturers used to select a default based on geography. In Northern climes they would use default to heat and in Southern climes they would default to cool. This saved wear on the solenoid and allowed the unit to function with a bad solenoid coil for the most frequent use (heat or cool). Lately the HVAC manufacturers do not base decisions on location or where it will be sold. So test your system and see if the O/B is energized when compared to the C (common or chassis ground at the 24vac transformer). Now check to see if you are getting hot air when set to heat, cold air when set to cool. If not then look in the thermostat setup guide to reverse the O/B function (change the default).

Does this thermostat run on battery or common run from the system?

the dual run capacitor is bad located in main panel of unit size of small red bull can it will be swelled up on top indicating it bad get on at electric motor or electric supply house most ac stores wont sell it has a rating like 35/5 370

Is it set on summer switch which is the fan running all the time blowing cold air

the issue is most likely not with the thermostat, set the temp down to 65 degrees and listen for a click at the thermostat (it may not make any sound). go outside where the condensor fan is and look to see if the fan is spinning. if it is then the thermostat is probably ok. If you still are not getting anycool air and just warm air pumping out you may need to have someonne come and check the coolant level in your system. It may just need a recharge, but if you have lost coolant there may be a leak in your system. Alll that being said, you may need a licensed professional to come out and check your system

If you are not getting a signal to your gauge, your car can still run. You just won't know if your car is overheating until it is too late. A bad thermostat won't keep your gauge from working. The temperature sensor that sends the signal to the gauge will keep it from working.

The thermostat helps your car in extreme weather. It helps your engine warm up in extreme cold so your heater will work sooner. And it helps you car cool itself off in extreme hot weather. As your engine water temp rises, the thermostat will open allowing the water in the radiator (that has been cooling) to flow into the engine block. The water that was in the block will go into the radiator to begin cooling.

In fair weather, you don't need a thermostat.

Let the truck run for about 15 minutes. If the engine temperature does not come up turn the heater on and check to see if the air coming out is hot or cool. If it is hot the engine's thermostat is operating fine and most likely the problem is with the temperature sending unit for the gauge. If the air is cool the thermostat is stuck open. Try replacing the thermostat if the air is cool.

Change your thermostat before it sticks closed completely. Sticky thermostat is usually the cause.
Another possibility is that your radiator fan temperature switch is going bad. This is usually located next to the upper radiator hose at the gooseneck on your engine where the thermostat is located.

Good day,
If the machine has been running at least 6 hours in cooling mode, and the thermostat shows open. It is defective, and needs replaced.
It is located in the freezer section behind the back panel, and is located on the top of the cooling coil.
Hope that helps.

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Either a bad interface\display board or a bad main computer. I would try the main computer first.