I just purchased this house and I am testing the furance. It looks very new. The AC works fine. The fan constantly run unless I turn power off to the furnace. Also, I just tried turning on the heat and the fan comes on high and it sounds like its running but no hot air.

Did you have the house inspected before your purchase?

Try to power off at breaker then turn back on. If that does not work call for On SITE service. The high efficiency furnaces can take special tools and knowledge to work on.

Usually this problem is caused by a
Defective ignitor or flame sensor or open high limit causing the blower to run all the time.

Does the circuit board show a blinking lite? If so how many blinks.

What do you mean by open high limit

What do you mean by open high limit

Basically what I said. Many times a limit control will open and this will cause the circuit board to keep the fan running thinking the furnace is having or had a overheat event. Some can be reset while others need to be replaced.

Can you read a wiring diagram? There should be one on the inside of your front cover. Look for the high limit. Jumper the limit and see if that doesn't fix your problem. If it does, turn off the furnace power and replace the limit. If it doesn't work, we will go to the next step.
If you are not familiar with wiring diagrams, you are best off to call a pro. It may cost some money, but you will be warm and sleep better at night.