Dodgy pressurestat ?

conikal

Recently had the pressurestat fail on my Isomac. ( contacts stuck together i discovered)
Replaced it with a new Mater 'stat and reset to normal 1.1 bar .
This worked fine for 2 weeks, then suddenly today, during a brew session, the pressure suddenly creeps up to 2+bar and the safety valve opens. The heater was stuck on !
After turning the m/c off for a few mins, and restarting,...all is working normally again ?
        How unusual is it for a new Mater P'stat to fail intermittently like this. ??
..And yes, i will be fitting another new one PDQ !

Koffee_Kosmo

I had a pressure stat on one of my machines switch ON/OFF intermittently but not stuck on as in your description I changed it with a factory replacement and never had that issue arise again KK

Lacehim

It could also be something going on electrically that is causing the Pstat to play up. Might be worth taking it in for a look over by a coffee tech.  I would be taking the replacement back as faulty if it did that.

conikal

Thanks for the replys. I found this interesting post from a tech guy on a  HB  forum......

....After spending 4 years, 24/7 operation, with a Mater pressurestat, I can definitely say the sticky diaphragm is not a sign of a failing stat. Mine got stuck in the first few months after I bought the machine. The spare I bought on the occasion is quietly gathering dust, and a couple of times a year I unstick the original stat. There's good news and bad news: The good news is that the diaphragm is made of aluminum and simply does not fail -- these stats wear out when the microswitch fails either because of electrical load in a few years (if it's switching the boiler direct) or mechanical failure after a decade (if it's only switching an SSR). The bad news is that the diaphragm sticks in the "heat on" position. This happens mostly new out of the box, on start up, or in a few hours after, since the diaphragm has had time to freeze in the "on" position. This happens regardless of the stats age; and we have lots of stories of people ordering new ones after an old one sticks and getting the same thing when they started the machine up. This means your safety valve will occasionally get a work out, and you'll get a heart stress test when the machine starts blowing steam. If your heart can't take the stress, get a Sirai and replace it every few years. You unstick the diaphragm by removing the adjustment screw and working the pin under it in and out with a needle nose pliers. When you hear the micro-switch click back and forth, it's unstuck.

Useful. ..but it doesnt say much for the quality of Mater pressurestats ! ::)

Lacehim

I never had an issue with any of mine over the years, but I suppose they make a fair few of these and a few will have issues.  Also like any component on a coffee machine they have a useful lifespan, just like the antivac, filters, seals etc. As I said, if it's a new pressurestat and not working you should be able to return it.  You shouldn't have to repair, unstick or whatever, anything that you buy thats new out the box.