Hi, I have one with the same problem. I reckkon it might havew lost its gas somehow . Looking for a leak this weekend and will pressurise with air to try and find it. If it is that I will find a way to solder and regas.
Please let me know if you find an answer and I will do the same for youu.
modarleyatlive.co.uk Good luck. Let me have your email address ols if you wish so I can let you know how I get on.
searching internet now, I do know they run on ammonia 110 grams according to the label.
Maurice Darley
May 2015