it took me a while to solve this problem and found a text in brackets that said when you reach a altitude between 6300 feet and 6900 feet dial the knob to zero then set upto the altitude you are going to like 28000 feet ,I done it once and had no diff in pressures and all was fine ,I checked the knob setting for the altitude to show and it did have the high altitude showing but after a couple of years I forgot the inbetween altitude to reset the knob and the imformation was on a computer I sold so it could be 6000 and 6800 or 9000 and 9600 ,Iam going to give it another go and hopefully I can find the right altitudes again in flight to make it work again ,if I do I will reply again ,I tried twice and gave up on it 6 months ago so here I go again
