I have a Kenmore Elite smartheat quiet pak dryer. Model # 110.85866400. The problem is when I push the start button it beeps 3 times and the display flashes PF... and does not start..?. We have replaced the control board and still... NOTHING!. If anyone could help me... I would greatly appreciate it.. Thanks soooo much!!

Check the thermal fuse. Remove the bottom front panel and it should be located right near the front on the duct coming from the drum (where your lint filter goes). It's going to have two small wires attached to it and is going to look like a white piece of plastic. The other part with two wires is a thermostat. Turn the breaker off to the dryer, disconnect those two wires and join them together. Wrap some electrical tape around them to prevent them from shorting to ground. Turn the breaker on and try the dryer again. If it runs... replace that thermal fuse. Also check your venting as poor or improper venting and subsequent lint buildup usually causes the problem.

Any idea how to get the bottom front panel off?

Yes. All the way at the bottom front you'll find 3 screws. Remove them and pull out and down from bottom.