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If it's an older card with limit that's high enough, it can help with scoring by lowering utilization.
You should check with prospective lender though because a lot of them will require AU accounts be removed for mortgage and/or mortgage refinance so in the end, it might be in vain.
+2 to the other replies on here.
If it helps your AAOA, it will increase your score, if not it may lower it,
And like the other poster said, some lenders want you to take off all AU accounts so they can see your "real score".