Sounds like a common problem, Graeme.
Trouble is with mine, I am not sure of the attitude of the adjusting plate relative to the hinged arm on the splines. If I don't manage to get hold of an original in good condition, I will need to get it repaired (not sure this is something I can do satisfactorily at home; I will probably need a machine shop to sort this).
Whatever solution, unless it is a good original replacement which will already be lined up correctly, I will need it to be adjustable so when I put the heater box back I can adjust it to the correct attitude.
Trouble is with mine, I am not sure of the attitude of the adjusting plate relative to the hinged arm on the splines. If I don't manage to get hold of an original in good condition, I will need to get it repaired (not sure this is something I can do satisfactorily at home; I will probably need a machine shop to sort this).
Whatever solution, unless it is a good original replacement which will already be lined up correctly, I will need it to be adjustable so when I put the heater box back I can adjust it to the correct attitude.