I assume that you are referring to strap-leaf vandas, which among the vandas is the least tolerant of too much exposure to direct sunlight. Exposure to to the sun, as in your case from 7am - 12 noon is perfectly ok as the sunlight strikes the plant at angle and the angle keeps on shifting so no single area is exposed for too long to cause burning. It is from noon onwards that could be your problem, especially if the tree it is mounted on, is very big and provides too much shade. BTW the key word here is light as opposed to sun. Lots of light. Here is a piece of advice I got when I started growing orchids, 80% of which were vandas then, ' Give as much sunlight as possible without burning'. To get the maximum exposure to sunlight, the plant should be mounted on the tree facing north or south.
As to fertilising I use foliar feeding with 21:21:21 fertiliser, 1/2 strength weekly and a 18;33:18 every 4th week, for all my mature plants. All my strap-leaf vandas flower on a regular basis except my V Robert's Delight 'Garnet Beauty, which at best, 2 times a year and not all these last 9 months. Two other varieties of Robert's Delight flower about 4 times a year. Apart from light, genetics do play a part in the frequency of flowering.