My Carrier 58WAV136 forced air heater's problem is as follows - Thermostat works fine, when desired temp is reached, the fan motor (blower) kicks on. Sometimes it stays blowing for a couple of seconds, sometimes a minute. Often, the electric heating element will heat up and the gas furnace will light. But, the system will shut itself off within a few seconds and will try all over again. The LED sensor will blink 3 times fast, then one time. I do not have the manual to look this info up. Thanks for your help

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 .

Look at your system. Does it have any blinking lights or LED error code? If a light is blinking, count the blinks to get the error code. Note: if you turn off the power to the unit, the code will reset. You may need to wait for the next call for heat to see the code.

Check your fan motor. If the blower isn't running properly, the furnace will shut off with an over-temperature issue inside the unit. You should also check the air inlet/exhaust pipe for blockages. (This could be a flue or two independent pipes.) Finally, the problem could be with the internal control board communicating with the rest of the forced air system.

You may need a service technician to fix the problem.

I hope this helps. Please add a comment with the make and model and any error code for more information.

Cindy Wells
(Last winter, my own house had the fan motor fail. It started as an intermittent failure to circulate the air and the combustion chamber getting super hot. Replacing that motor fixed the problem.)

How many degrees before it reaches desired temp, does it shut off? A thermostat is designed to shut the furnace off a couple/ few degrees before it reaches set temp. It has what is called a heat anticipater, which shuts the burner down, and lets the blower use the remaining heat from the heat exchanger to bring it up to desired temp making it more efficient. If it is more than a few degrees, replace the thermostat. You can jump out the red and white wires to confirm the faulty thermostat. If by doing this, the furnace never shuts down, until you separate the red and white wires. That confirms a faulty thermostat. Hope this helps someone.

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.

Fan control could be on summer switch. or af control not working keeping fun running

Hello there,
If the burner kicks on but the fan is not starting, then it simply means there is a problem with the blower motor. The problem most likely is that the motor is dusty and need to be cleaned out.
Once the motor sis cleaned out, have it greased and installed back and ensure the wiring is intact, then turn on the furnace and the fan will start to foll. If that does not solve the problem, then it means there is a problem with the blower motor and it meeds to be replaced.
All the best Elect_Comp

it could be the thermostat on the wall not working or the fan control is not working as it should also check to see if air filter is blocked

sounds like your plenum temp sensor is pooched. once your plenum gets to a certain temperature then a sensor closes, telling your fan to turn on, if the fan doesn't turn on then the flames will be shut off by the high limit switch witch prevents your plenum from burning up.

make sure the thermostat is in the auto mode if so it is more than likely the fan relay control some are built on the board some can be replaced separately

your sensor to the fan is stuck in the closed position. This sensor kicks the fan on when a certain temp is reached in the heat chamber. It opens after cool down and apparently is stuck closed.