Hummmm. Zounds ta me like it's gone titsup and needs replacing. Try one more thing. With the ign. switch "off", disconnect the gray wire on the back of it. If it still doesn't zero, I'd replace it.<br /><br />c/6<br />Hooty<br /><br />Just for grins, with the ign. switch "on", check the "I" terminal on the back of the gauge. You should have 12vdc there.