A 51m penalty attempt from Ihaia West was spilled on the line by Auckland wing Bryce Heem, setting up a perfect attacking platform for the home side with a little over 10 minutes to go.
West capitalised on a tiring defence, slipping through to put the Bay ahead 17-12.
They then tackled their hearts out as Auckland constantly threatened.
Loosies Tony Lamborn and Brendon O'Connor got through a mountain of work while West again showed he has ice in his veins, calmly guiding the pack around the park.
Man of the Match went to workhorse Mark Abbott, who again proved his quality.
Hawke's Bay Rugby Union CEO Mike Bishop said it was a marvellous effort from the troops.
"It was just a fantastic game from start to finish," he said.
"The 6500 fans made their presence felt and the atmosphere was electric."
The forwards were outstanding last night and in tricky conditions the backs handled things tremendously.
Mr Bishop was unable to name his man of the match, saying all 15 players were deserving of the accolade.
Hawke's Bay Rugby Union commercial manager Jay Campbell said it was a "sensational" performance by the home side. "I applaud the crowd, who turned out in pretty rotten conditions - they got them home," he said.
The Bay's final shield defence of the season will be against Waikato on October 9.