Nuova Simonelli Mac autofill circuit might be bad

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
cottonwoodcoffee
Posts: 3
Joined: 11 years ago

#1: Post by cottonwoodcoffee »

Hello - this is my first actual post here, but I have read a lot.

I am rebuilding a 1997 Nuova Simonelli mac cup single group. I've essentially been through every part on the machine. My last remaining issue is with the autofill. I have a clean fill probe and the solenoid for the boiler seems fine (I suppose not 100% sure there, maybe 99% sure).

The issue is that the boiler fills when turned on, but will not stop filling. I can get the boiler to stop calling for water by letting the boiler fill up above the fill probe and then turning the power off and back on. That makes me think the ground, probe, solenoid are all good. The machine will work like normal until the boiler level falls below the probe and then the boiler calls for water again and won't stop unless I cycle the power.

Am I right in suspecting the autofill circuit or am I possibly missing something obvious? Should I just buy a new circuit?

Thanks in advance and thanks for maintaining such a great resource.

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allon
Posts: 1639
Joined: 13 years ago

#2: Post by allon »

I'd first check to see if you have power at the solenoid. An easy test would be to unplug the solenoid. If the filling continues, it could be a faulty seal in the solenoid, or maybe the manual fill valve, if so equipped.

If the solenoid clicks off when unplugged and the filling behavior stops, then it could be the sensor, wiring, or the controller.

As a side note, if you are using distilled water, the sensor will not work.

One step at a time. Don't assume the controller is faulty.
LMWDP #331

cottonwoodcoffee (original poster)
Posts: 3
Joined: 11 years ago

#3: Post by cottonwoodcoffee (original poster) »

Thank you for the reply. I hadn't tried your suggestion, but I did tonight. Taking power off the solenoid stopped the boiler fill.

I'll see if I can figure anything out in the wiring.

Any other suggestions?

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allon
Posts: 1639
Joined: 13 years ago

#4: Post by allon »

Note that:
http://www.nuovadistribution.com/images ... manual.pdf

states:
"If the electrovalve of the self-leveling device stays open for more than 30 seconds, it is automatically disactivated; the LOCK led flashes and the level leds switch ON to indicate the fault"

If this is not happening, I would suspect either a short in the wiring, or the brain box has a problem.
I suspect a brain transplant would cost more than the machine, giving you a couple of choices....

1: install a switch to deactivate the solenoid and manually fill.
2: Find a Gicar of compatible voltages and install it only for the autofill. This involves a little rewiring, but the machine is a bunch of orthogonal systems. No reason a separate controller couldn't do just autofill while the other controller operates the rest of the machine.
3. Live with it.
4. replace the circuit (= $$$)
5. Attempt to repair the circuit. Could be as simple as a blown FET or busted relay.
LMWDP #331

jlhsupport
Posts: 87
Joined: 15 years ago

#5: Post by jlhsupport »

Check all of your ground wires and make sure there are clean connections to the frame and on any terminals. Also for the main cord, check the ground and then make sure the outlet is properly grounded. Had this happen to an Oscar once, and the culprit was a ground wire that was seemingly lost in a bundle of wires but not attached to the frame. Secured the connection and bingo!
Joshua Stack
JL Hufford

cottonwoodcoffee (original poster)
Posts: 3
Joined: 11 years ago

#6: Post by cottonwoodcoffee (original poster) »

Hello - I just wanted to update this thread and say that I fixed the issue. It was the autofill controller that was bad. I am not savvy enough with circuits to say why it was bad, but I bought a used controller off of ebay for $60 and that was all it took.

Thanks to the people that offered advice. I learned a lot trying to figure it out.

How hard would it be to troubleshoot the faulty controller?