Why does this happen?

Joe is it?What's the situation? Are you pushing it in the air? Going from one autopilot mode to another?

Hi yes it is Joe, I'm trying it in the air?Even the altitude doesn't stay or v/s in position or lit up>

Okay, so you take-off with or without auto-throttle (TOGA)? In other words, is the A/T turned on? Do you have the CMD A turned on? The A/T (auto-throttle) indicated with a little green light and CMD A is the AP (autopilot) main switch that indicates two yellow dots when it's turned on. With those two switches on, you should be able to use any mode on the MCP, except a couple for approach and stuff. Is your FMC programmed by the way?

yes fmc programmed and no AP at all for takeoff so no auto throttle.once airborne cmd A is turned on.

Okay, once airborne you turn on CMD A, however, no A/T used for throttle. You need to have A/T turned on to use SPD, VNAV, N1, Level Change, or Speed Intervention (if you have the 800/900).You can turn on A/T on the ground if you like. It can be on while you manually throttle up for take-off.

I do have 800/900 cmd A is on but A/T doesn't switch up.

So it won't stay on? What FSUIPC version are you running?

3.4 or 3.41

I've seen a couple of people having strange problems after getting the 3.41 FSUIPC. If you can, go back or make sure you have 3.4.0.0 in your modules folder.

Ok i'll try that I'll let you know tomorrow!

If that's not it, then I have no idea. I just know a few had some issues with 3.41, and I still have 3.40. No problems here :)Some others might have some suggestions too. Oh well, off to bed!

Also make sure you have switched on the generators on the overhead panel, the Gen1 and Gen2 switches.

Joe is it?Please! SIGN your name on EVERY post per the forum guidelines. EDIT: I saw Per Arild already gave you the answer. Your problem is not related to FSUIPC!You can't engage A/T without having your engine driven generators connected. The switches for these are on the overhead panel. You may also want to look it up in the manual.If I may be bold I would suggest you try reading through the manuals about the different systems, especially the MCP and AFDS modes. Another good way to familiarize yourself with the aircraft is to do the tutorials that can be found here in the AVSIM library or at the PMDG web site. Hope it helps,

Sorry about the signature i learned how to add it in now. Thanks for the heads up to the overhead panel i'll read up on it and play around with settings on the ground not in the air :)