Unit not generating heat -

Have you cleaned the air return filters ? Wash them, don't vacuum or brush them. It damages the filter screen. Sometimes a thermostat will be out by a few degrees. If the filters are clean, try turning the temp down a bit to 65 degrees and see if the air con shuts down. ( If your room temp is showing 70, it should switch off the machine) If it doesn't turn off, keep reducing the temp by 5 degrees at a time and wait a few minutes each movement to see if and when it shuts down. If the machine keeps running, I would suggest your thermostat is shot and you will need a new one.

Try cleaning the air filter. Odds are the motor is getting to hot and it has a safety that stops the motor from over working.

About the only thing that it could be is a dirty coil,or some one over charge the system, I have seen just a layer of dust cause the compressor to cycle off to its thermal over load. Clean the coil.

Here is what you need to do to make sure your system is charged correctly go to the furnace take the temperature of to supply temp and take the return temperature at the furnace. You should have 18-20 degrees temperature difference if your return temp. is 77 degrees you should have 57 to 59 degrees. If you dont have these temps your system either wasnt cleaned properly or not charged correctly. If this helps please rate me and do a testimonial.

Check and make sure the filter is clean. This sounds like a restriction in the system. If the unit has central cooling make sure ther indoor evaporator coil is clean at the furance.The unit may be cycling the burners on and off at the high heat limit , fan/limit control. You can also eliminate the thermostst from the furance. Turn power off at the furnace and disconnect the wiring from the thermostat. Jumper the red and white wire together. Turn the furnace back on. The furance should run in the heating mode. Try this and see if the problem is still there.

Try new air filter.Maybe going off on hi temp limit control ? Short run time.

Typical temp split should be 15 to 20 degrees. A 75 degree return air temp should be in the 50s. Be sure coils are clean , if in that range the machine can do no more. If it is not, you likely have a refrigerant issue.

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I was wondering the same thing about our unit until I found the specs online and read that it has freeze protection. When the temp goes below 40 degrees, the fan comes on to prevent damage to the unit.

Check and see if it is froze up. Check big line at outside unit for ice. check filter and replace as needed. Check outside fan to see if it is running. Wash out outside coil If fan and compressor are running and has hot small line at outside unit. If not froze up and coil is clean you will need to call in a pro. If compress over heated you may need to wait for it to restart if coil was dirty. Again make sure out door fan and or unit is running and clean.

heat pumps generate heat from compressing freon and take a while to generate enough heat to be useful. never expect robust heat from a pump like an oil burner or a gas furnace, but they do heat great and are cheaper to operate. do this . if you are still using an old mercury bulb stat change it to a digital one. this will hold an exact temperature and time off between cycles will be less and the indoor coil will stay warm between short cycles, with an old mercurry stat you set it at 70 and it may run up to 73 and stay off till 68. thats a long off cycle and when call resumes the coil has gotten cold and has to start all over again. also dont wait till it gets cold to run a heat pump. turning it on and off as it gets cold is not correct. you should select a temp ,usually 71 for heat and set it and leave it on to do its thing.you may want to check the charge. hot gas discharge is usually 100 degreees hotter than outdoor temps after 15 minutes run time. for example if its 40 outside the big freon line outside thats insulated should be about 140 degrees. or you can run it 15 minutes and grab it with your hand . it should be almost uncomfortable to hold any length of time. careful some get quite hot. you also have the option of hooking up the electric strip to automatically come on if you push the stat up 2 degrees hotter than the temp in the room. that way you get heat pump and strips till temp gets within 2 degrees of set point and the strips shut off and pump maintains.good luck