Blower motor never cycles off when in AC mode, even when the desired temp is reached

Automatic fan control not work (AFC ) fan works on temp rise cuts in and blowes hot air .It also has a cut off temp so if fan get too hot it shuts off .

You're talking 3 problems. The manifold doesn't ignite with gas even tho your pilot light is working? And the blower motor doesn't start at all? Normally the thermostat will sense the current v. desired temperature, you'll hear a little click or similar, then it will turn the burner on, then the blower will start automatically after that. In some cases the blower will cycle off and on, others just blow while the burner is on, then stay on briefly afterwards until the manifold cools.

If your thermostat allows you to turn on your blower motor (look for on/Off Fan) try that first to see if blower works at all. That will rule out the blower motor or switch. If the blower does work, then it's likely the thermostat isn't telling the furnace to cycle on and start the burners.

My bet is you may need a new thermostat. If you have the very old mechanical circular one it's worth replacing to get the savings from a new programmable one. If you do have a newer model, I'd still listen to see if anything is happening when you move the desired temp higher than the current. Or if it is programmable check or replace the batteries, reset it to factory default, etc.

The newer models are electronic and will fail over time, their 2 year warranties pretty much tell that story. May need to replace it.

Do NOT try to troubleshoot by messing with or jumpering the 3, 4 or 5 small colored wires (more wires if your house also has AC) coming out of the wall. They are usually connected to a transformer of sorts; thermostats are low voltage devices, but it's never a good plan to try to identify or solve a problem by guessing at options.

And replacing these thermostats is not costly and is very easy - just a few wires to connect, plug in some batteries and program days times and temps.

HOME A/C units are designed to shut off when the desired room temp is reached.it is called Cycling. when the temp control unit senses that the temprature is too high then it will turn the unit back on till it again reaches the temp it is set oto

thats simple. this is caused by weak power button of board. let me know if you dont know how to do this.

Hello, it could be shutting down on it's high limit switch due to a dirty air filter, dirty blower wheel, weak blower motor. Usually this would cause the furnace to shut down before it reaches the desired temp.

Sounds like the blower motor is getting hot and cycling on internal motor overload. Probably airflow or the blower bearing or capacitor. Turn off all power to the unit then you need to check the filter, Evaporator coil to see if air is getting through it. When checking the coil for a blockage you need to remove a side plate, it's triangular and check the entering air side of the coil to see if its blocked. You need a volt ohm meter with a micro-farad scale to check the blower capacitor and motor amps. You could have a bad motor bearing.

Hello, you have a bad relay on the intergrated control board. The only option is to replace the board.

you have a possible thermal overload problem in your furnace blower motor dirt will cause this problem when it doesnt allow air across the windings of the blower motor if not dirt the motors going bad and getting hot use a shop vac and eliminate dirt keep your filter changed and your evaperator a coil may also need checked for cleanliness this will require cutting into plenum my advice someone qualified and remember dirt kills

Hi there. I assume the indoor fan runs continuously until the house has cooled down. Clean the condenser. (outside unit)
Another possibility is that the system is getting low on freon. Check for leaks with soapy water at all joints and fix them.
Thanks
Paul

When the thermostat calls for heat it should run until the room reaches the temperature setting then shut off. Is the blower motor running and can you feel air coming out of the vents? It sounds like the blower is either not running or putting out enough air to keep the furnace heating. The blower moves the heat from the heat exchanger to the room, if it can't remove enough heat from the heat exchanger there is a limit switch that will shut the burner off if it gets to hot and that's what it sounds like is happening.