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Nuova Simonelli Oscar won't heat up! Help!

Postby samuellaw178 on Tue Feb 07, 2012 10:41 pm

I have a used NS oscar with Sirai pressurestat. It was working fine on the first day and the next morning I turned it on, the power light turned on as usual but the heating light didn't. And the water wouldn't heat up even after 20 minutes, no sign of heat at all.

This model doesn't seem like it has a safety thermostat. The boiler is the same as the one hereNuova simonelli oscar doesn't heat up, except that mine was a Sirai pressurestat:
Image

After did my researches and going through many threads, especially this:
Oscar heater won't turn on after descale - HELP

I did 3 tests:
i) pressurestat: I jumped the two wires that go into Sirai, no gain.

ii) Heating element: I used a home-made continuity tester, alarm clock, wires and battery, to test for it. The circuit was closed. I did unplug the spade before testing it. By any chance would I miss a malfunction in heating element without exact resistance reading(don't have a multimeter here in my apartment)? In this test, I let the wires going into the pressurestat remain jumped. Is that right?

iii) Gicar box: I turn the machine upside down, took photo and jot down which cable goes to which slot, and disconnected the Gicar box. Nothing seems burnt on the outside. Is there any way to verify it is ok? Except that the heating light doesn't turn on and doesn't heat, everything else is normal. Pumps, boiler fills etc.

Any idea what else could go wrong? I appreciate your help very much!
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Postby allon on Tue Feb 07, 2012 11:16 pm

You should get a multimeter. A cheap $10 will serve you here.

Measure the voltage on the heating element. Should be line voltage.
Unplug the unit and measure the resistance of the heating element. Should be in the 10s of ohms. You can easily calculate what it should be using ohms law.
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Postby erics on Tue Feb 07, 2012 11:45 pm

Any idea what else could go wrong?

Have you downloaded the manual from the Nuova Simonelli site? Are you using water that has reasonable hardness? If "yes" to the hardness question, your water reservoir should have two wires going to it. One is a connection to ground and the other goes back to the Gicar box to "tell" the Gicar that the reservoir has water.

If you are using ultra pure water, you likely do not have enough "conductance" to complete the OK signal to the Gicar. TEMPORARILY connect these two wires and see if that solves the problem.
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Postby samuellaw178 on Wed Feb 08, 2012 12:57 am

Allon,
Thanks for the suggestion. I might get one but I can't find anyone selling it here in the downtown. I don't have a car so that's basically limits what I could get. =/ I could buy it online, but then it would take a about a week to be here. :( I was hoping to save a few bucks and time by the assumption that continuity of heating element= element is fine.

Erics,

I was hoping you would appear because of your knowledge in the machines. Thank you so much! This version I had, was modified by previous owner so that it takes water from an external water container, not the normal water reservoir in the machine. So I can't find the two wires you mentioned.

The Oscar could still refill the boiler when it's low (by pulling the water probe very briefly). Would that indicate the Gicar is fine? As for water hardness, I am using pretty hard water I supposed, just for testing purposes. 150ppm according to the municipal. The probe could sense the water and stop refilling even when the water was mixed with 2/3 distilled water. I think I could safely eliminate water hardness as a cause.

I did go through the manual from NS website. It shows a safety thermostat there(above heating element) which is absent on mine. Mine is dated year 2008.
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Postby erics on Wed Feb 08, 2012 1:16 am

The schematic I have shows that the (former) wire from the reservoir goes to terminal 1 on the Gicar. So, making the ASSUMPTION (you know that can be a problem) that your Gicar wiring is similar, terminal 1 should be permanently grounded in your particular situation.

I realize that tracing wires on the Oscar can be a PITA but it would be helpful to confirm that the wire connected to terminal 1 goes to a good ground connection.

Disconnecting the water level probe tests only the autofill function of the Gicar which certainly appears OK (per your test).
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Postby samuellaw178 on Wed Feb 08, 2012 10:57 pm

Eric,
It was late yesterday and I only have time to look at the machine until now. You're right, tracing the wire in Oscar is a PITA. I looked at the terminal 1, the wire does lead to a ground terminal permanently fixed on the bottom plate by screw.

What else should I do next?

The next alternative is probably to disassemble the whole machine and put it back. But it really seems like a lot of work and will have to wait until the weekend. =/

One thing I am not sure, does continuity in heating element confirm that it is okay?

Later add: My machine is dated 4/14/2008. And the manual on the website was updated at 6/16/2008. Might be helpful?
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Postby erics on Wed Feb 08, 2012 11:17 pm

What else should I do next?

It certainly comes back to Allon's recommendations re a multimeter. The grounding lead in the power cord which enters the machine is attached to some terminal and you need to make sure that the terminal 1 wire and the main ground connection are either the same or are electrically identical.

There is a relay internal to the Gicar which provides power to the pstat and then on to the heating element when the Gicar believes there is water in the reservoir. Power to the pstat is from terminal 5 on the Gicar but remember my previous comment about ASSUMPTIONS. So, with power off and unplugged, make sure that terminal 5 has a good connection.
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Postby samuellaw178 on Wed Feb 08, 2012 11:44 pm

erics wrote:you need to make sure that the terminal 1 wire and the main ground connection are either the same or are electrically identical.


Pardon my lack of knowledge in electrical :oops: What do you mean the same or electrically identical? The wire connected to terminal 1 on Gicar was connected to main ground cord on the bottom plate. Is that what you mean?

You're most probably right about the wire lead. The wire to pressurestat is black and the one on Terminal 5 is indeed black wire. I unplugged, examined and replugged terminal 5, sadly still the same. :(

Can I ask about one more thing? I did the continuity test on the heating element, with the pressurestat wire unplugged. Weirdly, the circuit is still closed. I was expecting it to be open because the pressurestat circuit was open, no?

I guess I will have to go to Walmart this weekend and get a multimeter. :|
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Postby erics on Thu Feb 09, 2012 12:07 am

Is that what you mean?

Yes. By "electrically identical", I meant that it could be connected elsewhere as long as that elsewhere spot was also grounded to the main power cord.

The pstat circuit will always be closed until boiler reaches pressure. The best way to test the validity of the heating element is to disconnect any leads connected to it and apply the ohmmeter to the element terminals.

You could also temporarily unground the lead from terminal one (where it meets the power cord ground), power the machine up and alternately make/break the ground connection. You should hear a relay internal to the Gicar "clicking".
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Postby samuellaw178 on Thu Feb 09, 2012 12:27 am

I unground the the from terminal one and do as you suggested. I don't think I hear any clicking by making/breaking the ground connection. How subtle/loud should it be?
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