Milwaukee had been shut out through seven innings and faced a 1-0 deficit when Josh Prince drew a leadoff walk from Erik Bedard.
Prince advanced to second on a sacrifice from Logan Schafer, after which Bedard was replaced by Hector Ambriz.
Weeks greeted Ambriz (1-4) with a home run to left-center on a 1-2 pitch. Ambriz also gave up a leadoff homer to Aramis Ramirez in the ninth.
Houston went 0-for-6 with runners in scoring position.
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