Go here works perfectly
Edit: read in titanium backup in settings.
Too complicated for explain here but if you have access to ext sd card with other apps than u do not need my link but read I titanium under settings!!
It's something like Location Backup map and there u must see something like backup provider that's the one you have to point to ext sd card....
Sorry mine is in Dutch so idk the name but if u look there it will become clear.
Here you go:
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