Hi, I have an ideal ICOS which was installed about 8 months ago. Recently the needle on the pressure gauge on the bottom of the unit has started vibrating or flicking back and forth a little bit making a sort of tickling noise even when stone cold. I have done alot of work over the last few months installing new rads, TRV's all resulting in the system being repressurised via hosepipe to mains water a few times. Other than this work I cannot think what might be at fault as the system has behaved itself all the way through. The cold pressure of the sealed system is about 1bar which goes up to approx 1.5 to 1.8 bar when hot. Can anybody tell me what might be at fault?