ok I think I know what the problem is - see if I can determine it for you :)
in your xaml file where you want to use TextConvert, define a resource for it (if you do not, then I do not know why it does not work)
<Grid.Resources>
<Shared:TextConvert x:Key="TextConvertKey" />
</Grid.Resources>
shared as xmlns of course.
Then in the text box use it like:
Text="{Binding Path=hM1,Converter={StaticResource TextConvertKey},Mode=OneWay}"/>
EDIT:
, .
2:
am,
local: HealthTextConvert x: Key = "TextConvert"
. HealthTextConvert, TextConvert???
local:TextConvert x:Key="whateverKeyNameYouWant"
Text="{Binding Path=hM1,Converter={StaticResource whateverKeyNameYouWant},Mode=OneWay}"