hi i have a te magna and the aircon cuts out after like 5 seconds and the light in the ac switch starts to flash and ideas thanks

It is probably broken, borked, non functional. It is probably out of gas and the low pressure switch is cutting off the aircon clutch. Flashing light is to let you know it needs gassing up. A lot of people of older cars will find that when the warm weather comes, that their aircon isn't happy. There may be a sticker under the hood saying when it was looked at last, if not, it is the original factory gas.

it works some times just have to keep turning it on and off until the ac switch light stays on tryed to re gas it but the compressor wont stay on it keeps cutting out and the ac switch goes from solid green light to a flashing green light ?

Take the car to an A/C specialist, they will re-charge the A/C system with new gas and probably replace some seals and the inline filter while they're at it. Would be like $200-$300 or something I would expect, and then it will be as good as new.

Before you go spending cash, check that the aircon fan(s) are coming on when you turn the A/C on - if not, the hot gas does not get cooled and condensed resulting in the high pressure switch turning the compressor off. You can hotwire the compressor to over-ride the HI/LO pressure switch but check the fans first.
Good Luck.