Some users find that the when they activate the Auto Pilot the aircraft will go in to a steep climb or dive. This issue has been fixed in the Update 1 patch, so please install the update and then set the Invert Elevators setting to fix this issue.
To change the Invert Elevators setting, please follow these instructions:
Once you have installed the Update 1 patch for this aircraft please go to Start > All Programs > Wilco Publishing > 737 PIC, and then click on the specific configuration tool which matches the variation of 737 aircraft (such as the 737-300) which you are wanting to fly, and load up this tool.
When the tool has loaded you will see numerous tabs across the top. Please click on "Preferences" and then at the bottom of the page you will see a box with "Invert Elevators" next to it. Please tick this box, and then press "ok" to accept the changes.
If you now re-start Flight Simulator and select the aircraft (eg: 737-300) and you should find that the Auto Pilot now functions correctly.