I would greatly appreciate any help in solving this issue.
I recently purchased an older ECM Giotto with half moon dial. The machine was achieving 1 bar pressure for about a day, thereafter the gauge was only reading .5 with 1 hr warm up. I did 2 full descale regiments as recommended by the following site http://biobug.org/coffee/giotto/. The Giotto now fluctuates in between .5 bar & 1.0 bar. I can hear a click and it rises to 1.0 at a fairly decent rate, as soon as it hits 1 it slowly decays to the .5 mark and repeats the cycle.
My guess would be that there is a small leak somewhere? I did notice the vacuum breaker was making a lot of hissing and didn't seem to seat correctly. Also, the water sensor rod was not tightly installed (when I removed the water sensor wire it came up Little.) Are these seals/parts still available? Would replacing these be a good next step? Any recommendations would be greatly appreciated.

Your vacuum breaker may not be sealing. Keep in mind there is a dead band with a pressurestat. That is the delta between the heat on and off. Depending on the pressurestat you have, 0.5 bar could be normal, albeit a bit on the high side. The click you mention is the pressurestat closing and the boiler then heats to the top of the deadband then clicks to open the circuit and stop the heat. You may need a new pressurestat. You can try taking the pressurestat off, put a little descale solution into it and let it soak for an hour or two to see if that limbers up the diaphragm that controls the P-stat. If that does not do it, a replacement may be in order.

Thank you for the advice. I will go ahead and replace this pressure stat. I see one is available here http://www.chriscoffee.com/products/home/isomacparts/pressurestat. I am hoping there will not be a compatibility issue. My Giotto is an older one. If anyone has any tips on replacing this I would love to hear from you. Also, would it be wise to replace the vacuum breaker as well? Thanks again for your help.

You may want to open the case first to check it. I dont know if they used those small one or something like the Sirai's which are much more expensive and can be rebuilt. You can also take the vacuum breaker off and soak it in some descale to see if it seals up better. The rubber seal on them will harden over time. I keep a spare in my parts bin. They will sputter a little as the machine heats then snap shut. If it sputters after it closes then it needs cleaned or replaced.

Thanks you again, I opened the machine up and the pressure stat is a SOPAC PS 15.01 (CPH 0/9/1,7, CPH 13,9 24,7 psi). I suppose I will try to clean it first, as you originally recommended. If I do not see an improvement would the pressure stat at Chris Coffee be a drop in replacement. Or would it be a better idea to purchase another brand? Thanks for your help

Yes that is the pressure stat on my Giotto. I just now removed the pressure stat and the vacuum breaker. I also removed the gauge line. There is scale build up at the inlet of the gauge. I am soaking this as well as the vacuum break. I am not sure how to clean the pressure stat. Any suggestions?

I am not sure how to clean the pressure stat. Any suggestions?

Use a syringe w/o needle or similar device and "inject" some white vinegar into the port. While you have this pstat out, measure the threads - they are probably 1/4" BSPP pipe threads and you could check this by briefly hand screwing it into a easily found 1/4" NPT pipe fitting from the local hardware store.

This vinegar soak probably needs 30-45 minutes and likely should be repeated a couple of times.

Thanks you for the suggestion. I have injected the pressure stat with white vinegar. It sounds like it is getting inside as I hear the clicking as I press the syringe. I will do it a few times and let it soak. I will take the pressure stat to the hardware store to get the correct size when I am done. Thanks again for your help.

I soaked the pressure stat, reinstalled, and it is still doing the same thing. One thing I notice now since I have all the sides off . I can hear pressure being released from the safety valve. Could this be causing the problem? It hits that 1 bar mark and I continue to hear it until .5 mark. I did check the threads on the pressure stat and they are 1/4" BSPP.Thanks again for the help.