Order a Ceme from Jim as a replacement. You'll need two 11/16 or metric equivalent wrenches to replace the stat, and a jewellers screw driver to set it. The electrical connections go on COM and NC. The one I got was set to high, and you might want to give it a full turn before you install it. To set it, let the machine warm up with the bottom cover off, and the tank empty. If the pressure goes too high, unplug the machine, tip it on its side, set the pstat and repeat as necessary.

* Replacement part for espresso machines that have a small pressurestat
* Two wire connections occur at the 9 and 12 position when unit is situated at 9, 12, and 3 o'clock
* Available in 110 volt only
* Superior to cheaper MATER pressurestats due to fact that these have a stainless steel diaphragm
* Not a returnable item
* Technical support and instructions not included
* Please note that current stock does not have deadband adjustment as shown with offcenter smaller screw - in addition, the deadband adjustment if turned too much would render the pressurestat defective.
* WARNING: If your current pressurestat has limescale buildup, a new pressurestat replacement will fail within the first 6 months and as little as 1 month. therefore, if you see limescale, it is best to descale your machine prior to installation of the new pressurestat as we will not cover the warranty or replacement if the new one fails for this reason.
* WARNING: It is possible that you can adjust the adjustment screw too much, and this will damage the new pressurestat. Therefore, you should only adjust the center screw at maximum of a half turn increment after checking pressure on machine's boiler pressure gauge. If there is an offcenter screw, this one is more prone to damage and we strongly recommend not touching it. We will not replace nor warranty the pressurestat due to adjustment damage by the customer.
Is it true that either electrical connection can go to COM and NC?

howard seth wrote: However, the 'how to replace the Mater with the Ceme stat' instructions are not easy for me to understand. What is COM and NC?

another_jim wrote:In general, I don't encourage people who have no experience fixing things around the house from doing machine repairs; but I guess everyone has to start someplace.

There are two wires with slide on connectors hooked to two of three tongue-like connectors on a pstat. the ones you want are labelled COM (common) and NC (normally closed), the one you don't want is labelled NO (normally open).

0. unplug the machine, allow it to cool, and empty the water tank
1. remove the driptray, remove the Philips screw you see under the tray, put it on a box somewhere. Lay the machine down with the black plastic base towards you, and pull off the base (you may need to use a screwdriver or knife blade to lever it off, it fits snugly. You will see the innards of the machine displayed.
2. The Mater Pstat is a black cylinder with a small box attached, and two wires attached. It is mounted on an l-shaped pipe going into the boiler and is aligned horizontally. It is **not** the box connected to the flex hose from the pump; that's the boiler fill solenoid. See the pic in the review.
3. Have a rag or sponge handy. Use two spanners to open the fitting screw between the pipe and the pstat. Take off the pstat, wipe any water that leaks out. Then ease off the two wires.
4. Take off the little cap with the paint mark on the Ceme, and give the set screw a half clockwise turn (towards the minus sign embossed in the case)
5 Attach the two wires to the Ceme, COM and NC (which wire goes where is not important), and use the spanners to reattach it to the pipe.
6. Put the machine upright, add no water to the tank, don't put on the plastic base, and fire it up.
7. When it reaches the right pressure range, and if the pstat isn't switching off at the right place, unplug the machine, tip it holding the base and tank, and adjust the setting screw about 1/6th turn in the right direction, fire it up and check if it's right. Repeat until you have it properly adjusted. The Ceme has a .2 bar deadband, so ideally have it turn on at the bottom fo the green zone, and turn off at the top.
8. Put the base back, fill the tank, and fire it up.

If you don't feel confident doing this, give the instructions to someone who does this sort of stuff, it's not a tough job.

Now you owe me a good lunch

howard seth wrote:I suddenly seem to be having - as of last morning - a sticky pressurestat - problem as well - on my Elektra Semiautomatica. I descaled the machine tonight and the pressure gauge does now cycle off at about 1.5 - instead of going over the red zone- like it did this morning - however 1.5 is a bit higher number than before the sticky stat happened.

I see there is a move to replace the Mater with a Ceme stat above - but that sounds past my technical abilities -

I wonder what to do.

Meanwhile - I noticed that the descaler -Ascor DL- took the thin chrome skin off the inside of the water reservoir to the water line -( it looks coppery now) I diluted this descaler correctly based on the instructions that came with it. I did not run the descaler solution through the boiler/steamer - just the grouphead.)

Sigh, Making tea is a lot less complicated than espresso...

Howard