problem mixed gas regulator

[DEMPSEY]

I have 2 of these mixed gas regulators and both seem to have the same issue so wondering if it is easy to fix.
There is 2 blow off valves on the reg and when I turn on the gas and keep the outflow to the beer keg closed,one of the valve clicks and starts letting the gas bleed off. Thinking it is faulty I removed it and replaced it with one from the second reg only to find it is doing the same . Coincidence . Has anyone got an idea what's wrong. 

[magnethead]

Sounds like an internal one way valve/diaphram is failing..once back pressure builds up (you shut the beer side down) ...it can't hold and starts venting....

Looks fairly old  like my Regs!!..When you open your gas, do you crack it nice and slow so the needle rises over a 2 second period...or just let it rip where the needle jumps and smacks the diaphram...shorting it's life...I was doing this until I wrecked one Reg and learned...I imagine you're doing it right since you've been in the game

but what I really came on to say was, Give the customer support at http://www.jemphrey.com/ a shout ;p they support all the Norgren Regs and have techy people there
call us on 028 91 812000 (from UK and Northern Ireland)/ 048 91 812000 (from Southern Ireland) to discuss your requirements

Let us know, if they give you a solution

P.S...I would stick a gauge on a tee piece at the outlet to give you the Keg pressure ;p That's what I did