Upon purchase of a liquid filled air gauge, the user may find a variance in the readings from some known accurate gauge. This variance could be caused by the atmospheric pressure differentials from the outside air to the inside of the dial housing. This pressure difference, if great enough, can cause some gauges to read incorrectly as much as 5psi.

This pressure difference can be caused by the altitude being greatly different from where the gauge was assembled, transport via airplane, or simple travel from low altitude to high (sea-level to mountainous areas).

There is a simple way to correct this issue. If your gauge has a continuous rubber shock absorbing boot, carefully remove it. Now you should have the bare dial housing exposed. You will find a small rubber plug (normally at the top of the dial). Your gauge may also have the plug exposed via a pre-cut hole in the rubber booth.Cautiously remove this rubber plug and the gauge will equalize to atmospheric pressure. Replace the plug and rubber boot.

Your gauge should be fully operational within the manufactures tolerance.

Warning: If you have dropped your gauge or it has sustained a great shock or jarring, chances are your gauge it has been knocked out of tolerance (the internal components damaged). There is no recalibration for most gauges and your best bet is to simply purchase new one.