What kind of Mazda truck is it Candace ????? Is it the single or double cab pickup ???
If it is, it's probably what we call the Mazda B2200 or B2000.
If you do a search for those models, then you may find a schematic diagram, or alternatively, do a search on the Ford Courier.....exactly the same vehicle, as Mazda manufactured them for Ford.
I don't know if your model names are the same as ours, but if you search those models out, you may be able to bring up some Aussie sites that will help you.
I owned one of those for 15 years from new....I know a bit about them, but nothing really about the dashboard or the electrics behind.
Just a thought tho.....has he tried replacing the fuse ???? Or cleaning the fuse terminals.....that may be the problem....also loose fuse terminals can cause that problem.
Wom