The LCD screen is fine, the module doesn't get enough voltage due to the resistance in the battery compartment. All those Grandstand models have the contact issue. They build up oxidation on the contact fins, and they lose spring tension with every battery change. In order to make it work you have to remove the oxidation with some 800 grit sand paper, and you have to bend all 4 contact fins towards the battery by about 1 to 2 mm.
The LCD screen is fine, the module doesn't get enough voltage due to the resistance in the battery compartment. All those Grandstand models have the contact issue. They build up oxidation on the contact fins, and they lose spring tension with every battery change. In order to make it work you have to remove the oxidation with some 800 grit sand paper, and you have to bend all 4 contact fins towards the battery by about 1 to 2 mm.
Great info! I will give it a go.