I received a b&m psi gauge and it was thought to be broken and I put 40 pounds of air from my tank into the gauge and it read it accurately, does this mean the gauge is fine ?

 

i mean...why did you think it was broke?

put it in the car and see

 

A buddy of mine gave it to me for free, he said his buddy gave it to him because it was acting up, it seemed fine with the air pressure. When I install it, how will I know if its broke, does the gauge act all up.

 

well if it showed 40 when you put 40 in then......? whats the problem