Central locking and the weather!

I have a real strange one here, my central locking works perfectly when it is cold but stops working when the sun is shining or it is warmer,I cant think what would be heat related,any help would be appreciated.
Many Thanks
Gareth

Firstly check for dry mechs in the doors, but 9 times out of ten it's a sign of door actuator coil failure. Hope it's the first one

Hi Spud,I have narrowed it down to the drivers door as if I turn slightly back toward "lock" I can get it to unlock,what usually happens on the actuator and is it just a case of lubricating or will it need replacing?
Gareth

Would prob say try lube first, likely you will have to replace though.

Spot on Spud,duck oil did the trick,couldnt quite understand how it always locked when operating the inside button but the key wouldnt unlock it until you turned it back to the lock position ever so slightly..weird but lubricating it worked anyway.

Gareth