How to check if my boost gauge is really dead or not?

[SwitchSkier]

I finally had some time to setup the wiring for my Autometer Phantom electric boost gauge. I found all the proper wires and taps, but the gauge has no readings at all. It will not move. I pulled the plug from the back of the gauge and used a voltmeter, and it is getting good ground and switched 12v. Could the gauge be dead? The sender unit messed up? Is there a way to test those 3 wires coming from the sender? What should they read?

 

[crensinivon]

If it is 3 wire, check the signal wire to ground with the car off. Then check the car with it running the signal should change. If not check the three wires to where you tied them into the vacuum system and see what happens. You could also apply 12v for a brief second to the signal wire and see if the gauge jumps.