Yes it can be tested and not a roll of the dice under normal circumstances. The actuator can be tested on its own, after being mounted in the 3rd, and after the 3rd is installed in the axle. Instructions call for it to be tested in the 3rd while on the bench. This was done, but unfortunately it took a few uses to work the damaged O-ring out of its groove, so they couldn't have caught it during install.
What the instructions don't call for is performing a leak down test, which experience now indicates is a good idea on an air actuated locker to ensure the actuator will hold air for a given period of time(...as long as possible). I made pressure tester and gave it to the tech to use to make sure we had a good seal on the bench and again after the 3rd was installed.
After going in a 2nd time to fix the actuator, the final $$ tally is that I spent $1000 to save $500 on this locker closeout deal. No net savings, which if I had it to do again I probably would have chosen a Harrop (Eaton) E-Locker-, magnetic actuated so no compressor required (saves $500+ and the install, plumbing time), or an even simpler Detroit (Eaton auto locker).
Re Side Note: Happy to take the lead, as long as you're spotting for me.
Here is a pic of the leak down tester I made- copied idea from one I saw on gearinstalls.com.
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