MGD Senior Member Joined: 11 Oct 2011 Posts: 16 Location: MA Expertise: I love coffee
Posted Sat Mar 31, 2012, 6:22pm Subject: Oscar NS not heating up
Could anyone point me in the right direction concerning my machine? The machine was working just fine until I started to notice a few quirky things.
I developed vapor lock to the point where I consistently had to make sure and open the steam valve to equalize the pressure in order for the machine to warm up and produce steam, something I never had to do before in the 3+ yrs of owning the machine.
After making an espresso or while waiting for the machine to warm up (purging it and opening the steam valve), it almost seemed like the pump would turn on in a normal fashion to top off the boiler but more than usual in short intervals?
While making an espresso, I would hear the release of pressure which after making a cup with the top of the machine off, I identified that it was being released from the pressure relief valve on the top of the boiler.
ALso while the machine was warming up, the temp switch would turn on and off repeatedly and eventually stabilize/remain illuminated indicating the machine not ready for use.
I noticed that the steam pressure was not quite at its maximum i.e. there was a slight loss in pressure.
Finally, now when the machine is turned on, the temp switch does not illuminate at all from the start.
germantownrob Senior Member Joined: 2 Dec 2007 Posts: 2,008 Location: Philadelphia Expertise: I love coffee
Espresso: Duetto 3, A Dead Oscar Grinder: Vario-W, Preciso w/Esatto,... Drip: Brazen Roaster: Diedrich IR-1, HT B
Posted Sun Apr 1, 2012, 6:25am Subject: Re: Oscar NS not heating up
Have you ever descaled the machine? Scale build up on the fill sensor at the top of the boiler can cause issues I have read, I descale every 6-9 months so I have never had this issue.
The Pstat controls turning the heating element on and off, after time carbon can build up on the connections and it stops working proper. The good news is the Sirai Pstat has three connections so if one has failed you have two more to use. I had the pstat stick in the closed position which kept heating until the pressure valve popped but the machine had heated so hot that one wire burned through and I had to retire it. The next connection failed in the open position so the machine would be cold at times when I walked up to it, this was a slow failure and didn't realize what was going on for a couple of weeks. I replaced my pstat, the tech at Chris' coffee felt my original pstat was somewhat faulty and should have lasted longer, the rlacement has been in for over a year with no issues so far.
Edit: when my connection failed open on the pstat a slight rap on the side of the machine would make it close the connection and start to heat. It is not difficult to move the wires to the next connection which will allow you to check if this is your problem or not.
MGD Senior Member Joined: 11 Oct 2011 Posts: 16 Location: MA Expertise: I love coffee
Posted Sun Apr 1, 2012, 7:36pm Subject: Re: Oscar NS not heating up
Sorry, On my model the PSTAT is located on the top left and it is a CEME. I just turned on the machine and the water temp light lit up. There was no noise from the machine. I opened the steam valve and ran some water through the group head. Soon after I heard a clicking noise and the water temp light went out. All of this happened in a matter of less than two minutes from turning on the machine.
MGD Senior Member Joined: 11 Oct 2011 Posts: 16 Location: MA Expertise: I love coffee
Posted Sun Apr 1, 2012, 7:56pm Subject: Re: Oscar NS not heating up
I guess I am just confused. What I just referred to is actually a solenoid valve according to the diagram from the NS for the Oscar model. The noise that corresponds to the turning off of the temp light comes from a large black box that has Sirai written on its side which I thought was the brain box and is located above the boiler on the right hand side.
germantownrob Senior Member Joined: 2 Dec 2007 Posts: 2,008 Location: Philadelphia Expertise: I love coffee
Espresso: Duetto 3, A Dead Oscar Grinder: Vario-W, Preciso w/Esatto,... Drip: Brazen Roaster: Diedrich IR-1, HT B
Posted Mon Apr 2, 2012, 5:25am Subject: Re: Oscar NS not heating up
MGD Said:
I guess I am just confused. What I just referred to is actually a solenoid valve according to the diagram from the NS for the Oscar model. The noise that corresponds to the turning off of the temp light comes from a large black box that has Sirai written on its side which I thought was the brain box and is located above the boiler on the right hand side.
The black box that say Sirai on top of the boiler is the pstat. The black cover has a screw to take it off( do it unplugged as you will have to take the electrical connection in front off to get the cover off). Under it you will see the electrical connections, the points that open and close to turn on the heating element, and a screw that can be turned to raise or lower your boiler pressure (temp).
Have you ever run descale solution through your Oscar? Depending on how hard your water is 3 years is a long time for scale to build up in the boiler and through the HX tubes.
MGD Senior Member Joined: 11 Oct 2011 Posts: 16 Location: MA Expertise: I love coffee
Posted Tue Apr 3, 2012, 7:19pm Subject: Re: Oscar NS not heating up
Ok, I switched the wires on the pstat to the next set of connections. Still the machine does not heat up. I did not bother to check the third option. THis is what happens... turn on machine and no heat switch light nor noise. Open steam valve and heat light comes on, water from the steam valve comes out and the pump kicks in both pulsing in synch water, pump, and heat light until the steam valve is closed then no action. The other thing I noticed, is that I am getting some water leaking from my pressure relief valve ontop of the boiler. WHat do you make of this? Thanks again for your help.
dyno Senior Member Joined: 20 Nov 2011 Posts: 41 Location: Burnaby BC Expertise: I love coffee
Espresso: Oscar Grinder: Super Mini / Super Mini E
Posted Wed Apr 4, 2012, 3:22pm Subject: Re: Oscar NS not heating up
I would probably replace the pressurestat altogether. The CEMEs were known to be problematic in the earlier versions of the Oscar so were replaced with commercial grade Sirais. But even those, with age, can fail - something to do with the diaphragm breaking down or stiffening. Switching the leads wouldn't be a fix in that case.
My first Oscar would only heat up partially....never to the point where it would produce steam. A new Sirai stat fixed it and was easy to install.
It also wouldn't pump/prime so monkeying with the leads as above seemed to solve the problem. There was a fair bit of corrosion when I got it so the fix wasn't surprising.
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