Recently I have started having trouble with the autothrottle engaging, actually not engaging. I start and push and while taxiing to the active try to engage the autothrottle and it will either not engage or engage for a second or so and then disengage.Any thoughts/suggestions are appreciated.

???I assume you mean "arm" rather than engage, which would be a lot less exciting. You haven't provided much info, have you set up FMC performance and takeoff including V-speeds? Does the FD engage? Does the FMC takeoff screen indicte preflight complete?

Sorry Dan for the lack of info and yes I should have used "arm" instead of engage. This problem started happening off and on just after purchase of PMDG in March. I would swap a/c to something like the Lear and come back and the autothrottle would arm. Then it started arming for a sec and then disarm and after pushing the switch several times it would remain armed and now none of these work arounds are working. Everything else is complete. V-speeds, takeoff runway and such all complete. Thanks for your time.

Ms/Mr Nameless,Please take a minute to read the forum guidelines. You need to sign your posts with your real name. Thanks. You need to make sure your electrical systems are properly set up otherwise your A/T will not arm.Hope it helps,

Try flicking the APU GEN switches to on in the overhead.They are spring loaded so will return to their origional position once flicked.