I have a Carrier 8000 furnace. The furnace will run fine for days or even weeks at a time, and then the code comes on that the pressure switch is stuck open. I can flip the breaker off then back on again and the furnace will work fine for awhile, and then start giving the same code. Any help would be appreciated. Is there a reset switch and if so where is it? Thank You.

It says the pressure switch stuck open so that is what it is.

You can remove the tube from the pressure switch and check for water. You can also blow in the tube to make sure no water is present.

If that fails you could test the pressure switch but it is probably defective and needs to be replaced.

If the pressure switch tubing is clear and you have no obstructions at the pressure switch or at the collector box I would say you have a bad switch. It's a cheap part to buy and its not uncommon for a switch to go bad.

Any idea where the pressure switch is on this model?

On the inducer housing just bellow the inducer motor. It's a small round disk with a rubber hose an 2 or 3 wires going to it.