Boost gauge not at "zero" when not connected
 

Just bought a Blitz boost gauge. Straight out of the box, the needle isn't at "0", its showing a vacuum of 10cm Hg. The supplier says that when connected up it will zero, but that doesn't make sense to me. Surely with no +ve or -ve pressure being applied it should be zero?

My Defi one was the same. It did zero when connected, and works perfectly now.

My supplier said the same as yours, and added that if it didn't work once connected, to return it for exchange, but there was no need.

Connect it and see.

Alcazar