Whilst running PMDG 737NG 600/700 in Flightsim 9 (FS2004) I am unable to get the AP to work correctly. Upon activating the AP after take-off the VNAV and LNAV buttons have a mind of their own and will not lock into the flight plan which had been programmed into the FMC. On occasions they will illuminate for briefly, sometimes long enough for me to believe it

Please sign you full name to posts in this forum.VNAV will not arm on the ground. If the runway heading is not on an intercept course with the first fix, neither will LNAV be able to guide you. Of course, there is no autopilot below 400 AGL.

Hi,If your flight plan was correctly entered in the FMS, you still have to make sure that your plane is configured correctly, ie :- generators on- Flight director on- Auto throttle on (not absolutely necessary but then you're all set for an auto flight).Sorry if this seems obvious but better check that first, especially the generators...Bruno