What's wrong with my kegerator??

If anyone has some suggestions as to what's going on with my kegerator I would greatly appreciate it. I converted a chest freezer to a 4 tap kegerator about 3 years ago and it has worked flawlessly until a few weeks ago. I purchased a 4 keg secondary regulator panel from micromatic (each has its own separate gauge), which worked great until recently. Essentially, 3 of the 4 regulators work fine, but the 2nd one from the left no longer lets Co2 flow through it. Anything I can do to test that individual regulator to see if there is something in it to fix? I'm sure its not the ball lock gas fitting that connects on the in side of the corny keg as I replaced that. There is a black pin on the underside of that fitting and on the regulators that work, a brief shot of CO2 is dispensed if you manually push it in, but no CO2 release on the suspect regulator.

Does the gauge on the faulty secondary regulator follow the pressure adjustment knob/screw, or does it read zero the whole time?

And does each regulator output have a check valve or no?

Cheers!

Thanks for the reply. Each secondary regulator reads zero the whole time. Not sure if each regulator output has a check valve or not. Here's what I have:

http://www.micromatic.com/draft-keg-beer/regulators-pid-8241.html

That's a sweet looking panel.

I honestly don't recall a situation where a regulator didn't provide at least some throughput. I've seen plenty where a regulator wouldn't shut off, or crept up in pressure, or had the PRV valve go off, etc.

My thought was perhaps you have a stuck check valve on the bad regulator. Unfortunately the site doesn't mention if the shut-offs have integrated check valves. And you can't tell from the picture.

You can find out by disconnecting the tubing from the barb, opening the valve all the way (shut off the tank first! ) and shine a light up the bore of the barb to see if there's a check valve ball, or if you just see the ball valve (twist the valve handle to check what you're seeing).

Cheers!