Boost Gauge and Shop Class

[onthetrack01]

I have a boost gauge (from a '90 SE) that I believe is on the fritz (engine boost is fine, but gauge stops when it hits exactly .5 bar - gauge works fine below .5 bar). I'm sending it to a gauge shop, but the shop needs to know what level of electric resistance is represented at each mark on the gauge. Anyone have ideas on where I can get that kind of info? Thanks!

[cnh1990]

Did you check the transducer on the right rear wheel butress?