Velux window won't open fully

[BazzaS]

I've a velux window in my pitched roof. Its operation is via a 'bar' across the top of it - partly open the bar and just get air-flow, fully open the bar and the window is unlocked and can be swung open. At least that's how it has been for the past few years. The other day I did this and the window will only swing open about 3 inches. There's a definite something stopping it opening further. Looking up at it from the outside in the garden doesn't disclose any obvious obstructions. My family all deny any clunks or noises - 'it just became like that' (!??). Anyway I'm flummoxed.
All and any advice gratefully received. (and no, I won't be going on the roof to look closer)
Thanks

 

[masona]

Is the locking bolt sticking out?

 

[BazzaS]

No sir, the locking bolt is fully retracted into the frame of the window.

 

[masona]

The problem would most likely where the centre pivot hinge is

There should be a pin on the hinge which need to be push in and swing the window right back to you and take the window right out and then investigate what the problem is.

 

[BazzaS]

Thanks for that - but unfortunately I cannot get the window open far enough to disclose the pin you speak of. From the inside, sliding and jiggling a thin blade (e.g. a skinny scraper) along the gap between the partly open frame of the window and the window frame itself doesn't indicate anything like an obstruction that I can play with.

 

[masona]

Get another person to help you, open the window and keep banging it although you're trying to open it, run your hand over the frameand you should feel the most vibration area point to indicate where it's hitting something

 

[BazzaS]

Thanks for your advice. Whilst giving the window a persuasive bash it opened a bit and then a bit more until it was fully open! What a berk I am. What was 'blocking' my window opening was muck and I was too scared to give the window a good push just in case it was a mechanical problem. All hinges/pivots and the like are now pristine clean with a smear of grease and the window is operating fine now.
Once again ta.

 

[masona]

From the Velux website;

It is recommended that non corrosive grease be applied once a year to all hinges.

Got to do my 5 velux windows and one of them I can't reach