Guessing it is 2006
Thank you - the arm is not split, so will try the wash and jug of water.
The seals (a peculiar 2-holed silicone type rubber washer that 'floats' in the grey plastic case) where the top arm pipe engages on the top water feed do not seem very tight - is this normal?
Tried the jug of water and it cut in the discharge pump within about a litre. There was already water all over the bottom pan of the machine, so I don't think low water level is the problem. Took off the lower arm and switched the machine on then opened the door and there was a healthy fountain of water squirting vertically up to the top tray. However, placed objects on both upper and bottom trays so as to foul the arms after half a rotation (having established direction of rotation) and then timed to see how long it took for the arms to get around - it was nearly a minute, which seems excessive. So is it a case of high water volume but low pressure from the pump?
This is for both arms - each arm took that long to rotate. Then I noticed that one of the end spray holes was blocked, which I'm sure was clear when I previously inspected it, and managed to get out a large seed covered in fat and subsequently 4 or 5 others! So I presume the fat is gumming it to the arm so you cannot see them and then they dislodge and get stuck in the spinner hole. Am just running the machine without the spinner arms to try and dislodge anymore seeds that might be in the system. If this does not work, we will remove side panels to look at the heater as requested.
The heater is working because the water is now warm in the cycle. Arms blasted with the garden hose and are now rotating in about a second! So I think we have solved the problem - thank you and I feel a bit stupid!!