Full sweep gauges will not full sweep on power up! Why?
This is a question/concern that we hear more often these days as many OEM, and some after market gauges perform a full sweep on power up. Auto Meter full sweep (digital stepper motor) gauges will not perform a full sweep. Instead what they are intended to do is a “calibration sweep” which is a little different. Instead of sweeping to full scale and back, the Auto Meter gauge(s) will simply sweep backwards from its last reading to just below the minimum reading, touch the stop pin, then go back up to whatever current reading is. If the gauge is already at minimum reading, you will then see little to no pointer movement, however you may hear a momentary buzz, or grind noise as the stepper motor tries to push the pointer against the stop pin. This is completely normal.
Here are a couple examples: If you shut your engine off and your oil pressure gauge stops at 40 psi, the next time you power it up, the pointer will move down (backwards) to the stop pin just below zero, then back up to current reading when the engine is started. There is no full sweep on power up. If your gauge (lets say a temp gauge in this case) is already on 100 (minimum reading) because the last time the car was run, it was not warmed up. When you power the gauge on, the pointer will simply push back against the stop pin, make a momentary noise and stay there until the sender/engine is warmed up. Again there is no full sweep.
The only exception to all of this, is the (now discontinued) Auto Meter Nexus series. This was a series all by itself that had the a full sweep programmed into it as part of its “opening ceremony”. This opening ceremony, or full sweep can not be programmed into any of the other Auto Meter gauges
The pointer will move backward to the stop pin and then move to the zero box. This procedure is an auto-calibration
function and is performed on every power-up. While this test is being performed, the gauge may make a clicking
sound. This is normal.