Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I recently received an Allchin that was showing the same thing. Suspected part of the sight glass connection was plugged, so I removed the top plug screw from it and found nothing wrong. But, when the plug was removed, the glass showed the correct level, (SV removed during all this). Removed the bolt from the banjo fitting at the boiler, (where the pressure gauge siphon connects), and found that this hollow bolt had no hole near the head so the top of the sight glass had no communication with the boiler! Carefully drilled a hole similar in size to the one in the bolt and the gauge works now.

Hope this helps.