Sounds like what happened when my monovalve piston diaphram failed. You can search these threads for this topic for more info. If you would like send me your e-Mail address and I will send you the procedure for finding the monovalve, inspecting, and repairing it with some helpful pictures. But its only -10 C so your probably in no hurry!!!!!
Use the PM - private message - feature in the lower left of this window to get me your e-mail address!