I'm restoring a Gil. AM-11 air meter. Just finished testing it.... Tested and calibrated fine, other than when you set it at 50 PSI( or so) or greater. The air continues to flow through, but the main valve, doesn't trip anymore.

When I took it apart, I noticed the piece that covers the wheels, had " For Trucks Use Gauge" written on it. Was this written on there for the reason, that it didn't stop at the pre-set pressure above 50 ?..

I also noticed that on Jack's website, there is a pic of a diaphragm spring and disc, that wasn't in mine when I tore it down. Is this spring and disc, to solve that problem.

Any insight would be appreciated.
Thanks

Tom