You basically connect the mityvac securely to one hose at a time using a length of rubber vacuum hose. Pump it up and watch the gauge. The vacuum element should do its thing, and then hold vacuum.

Example, open the fuel door, and connect to the lock line for the fuel door. Pump up the vacuum. You should see the little rod come out that would stick through the hole in the door, and then hold vacuum. Same for the unlock side, but the rod pulls back. If an element won't move or won't hold vacuum, it should be replaced.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe