garry1p wrote:
Sounds crazy but try this (if you are using polarized sunglasses).
Looking through your glasses and rotate them to the right then rotate to the left.
One direction will black out the screen the other will lighten the screen up.
The GPS screen is polarized in a different direction than your sunglasses than the GPS.
I have worked with electronic surveying equipment with LCD screens and wearing polarized sunglasses. They are not a good mix. At first I thought there was a problem with the screen until I removed my sunglasses.
You may possibly have a defective screen also.