Had the same trouble. Dealers just kept dreaming up a number!
Does the light flash all the time? Does the light stay steady when you first start the engine - cold start, then blink?
In the under bonnet fuse box there is a relay for the aircon. Normally cream/white you can pay Toyota $75+ for a new relay, or you can go to Jaycar & buy the same relay for about $6.50!
Jaycar's part is the same rating.http://www.jaycar.com.au/productView.asp?ID=SY4045
See
Fixed my system - over six months now &cold as!
