Sunroof, HELP!!!

[oily]

Ok guys, here's the problem, my sunroof would only open about a third of the way and then the motor would run out of puff (so I thought) and the tilt facility would not work at all, so yesterday I decided to investigate. With the sun shining on the beast all day, everything worked perfectly (much to my surprise), so while the sunroof was open, I took the opportunity to clean and lube the slides etc. I had a wonderful time playing with it (the sunroof) all afternoon and it worked perfectly. I even played with it (the sunroof) on the way to work last night (life was wonderful again). Imagine my horror when driving home this morning, I decided to have a little play with it again (the sunroof) and feck, It was back to square one, only opening a third or so then the motor was struggling. the tilt bit still worked though. C'mon guy's, what do you think?. Could it be a weak motor? but why did it work perfectly yesterday?. Could it be misalignment of the tracks and after the sun had been on it for a few hours, the expansion of the roof sorted that out. I'm clutching at straws here and could do with some ideas

[oily]

Just been out to investigate further and guess what, it works perfectly again now. It defiantly performs better with the engine running, i.e. quicker and smoother. Could this be a battery issue? how do I check the battery with a multimeter?. I realize just checking the voltage wont tell me if it's a good battery or not.

[si tate]

Just been out to look at mine, with engine running it all works fine, but with engine off its dead slow on slide but ok on tilt, maybe they just need more power to slide or weve both got fcuked motors.