thanks for posting back, the unit come built and just said make sure the north mark on it is pointing to the north.....just my luck its made wrong and they have put the vane on wrong. I will get it back down in the morning and run some test on it., going to stick a fan next to it blowing from the north and see what the reading is before I start to take it apart., I was sure I was going mad. had a Davis years ago but it seems I have forgot how to use a vane now (miss my davis ) ,lol