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Installing A Wiper Door Vacuum Circuit Vacuum Tap

Mar 9, 2009
Right after I bought my '71 I had problems getting my headlights and wiper door to operate correctly because of a vacuum leak. To make the troubleshooting easier I installed a 3/16" steel tubing vacuum tap into the steel tubing wiper door "feed" line between the reservoir and the wiper door actuator. With the 3/16" vacuum tap installed I can easily connect a vacuum gauge to the tap, plug the hoses going to the headlights, then determine which circuit is leaking.

I began having vacuum problems right after I rebuilt my engine so I plugged my vacuum gauge onto the vacuum tap while plugging the headlight vacuum lines and quickly found it was the wiper door circuit that was leaking. Knowing it was the wiper door circuit causing the vacuum loss I quickly found it was the wiper door relay valve that had gone bad. So the vacuum tap made it a lot easier to find the source of the leak.

To install a vacuum tap into your wiper door 5/16" O. D. "feed" line just drill a hole into the top of the steel tubing using a #13 drill bit (.185") then sweat-solder a short piece of 3/16" steel tubing in place. Then place a rubber cap on the vacuum tap. It's easily done and once it's installed it's there to be used again and again.


  • 1971 Corvette Wiper Door Circuit Vacuum Tap 010.jpg
    1971 Corvette Wiper Door Circuit Vacuum Tap 010.jpg
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