the one piece of info you haven't given is how long you've had this tree and how long its been in the same pot. This is a small tree, this plant - it wants to get 5 metres high by slightly less width, and it can't do that in a pot. If its been in the same pot for longer than 18 months, a year if the pot isn't large, it'll have run out of root room - that means the ratio of root to potting compost is out of whack, and there's not enough soil to hold onto the water for very long. Increase watering and think about either planting it in the garden, or getting a larger pot.

Might be better in semi shade too.

I've had to move mine into the shade as leaves crisped up and they seem to prefer the shade and new leaves have grown too on one of them :o) Also I agree with what Bamboo has said :o))

Acer negundo is a riparian tree in it's native habitat, and it is almost impossible to overwater it.

Thankyou all for all the advise , I will certainly put it to the test and watch my Acer revive, thanks again.

Good luck, Ian!