Auto-fill not stopping - Bad controller?

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by LoudonMiller »

I'm finishing up a complete refurb on an old Simonelli MAC. But, the auto-fill is overflowing the boiler, and I can't get the fill-probe/controller to turn the pump off.

I jumpered the auto-fill port on controller directly to the incoming ground. I believe this should have stopped the pump, however it keeps running.

The controller works for everything else (so far): power on, open boiler fill solenoid, open group head solenoid.

Any ideas? I've invested $100 total and I don't think a new controller is in the budget.

User avatar
BaristaBoy E61

#2: Post by BaristaBoy E61 »

You might try switching the pump relay with another to see if anything changes.
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"

LoudonMiller (original poster)

#3: Post by LoudonMiller (original poster) »

No luck on switching the relays. #3 and #5 open the pump and boiler level solenoid, but neither respond to closing the ground on the auto-level circuit (and I tried both the connector and by touching the board contact directly).

Anyone have a thread on converting something like this to a manual operation machine?


#4: Post by jpboyt »

Try jumping the pin four level sensor wire to the pin two ground wire and not the machine ground. This is the path of least resistance. You can loosen the four pin Phoenix connector and insert your probe wire. This should shut the water off. If it still runs on then measure the resistance of pin two to the top of the 7805 voltage regulator. Heat sink lug is ground plane for the board. Should be a couple of ohms at most. I have seen boards get corroded and have the ground pin not be conductive to circuit board. Since the ground pin is also being used for the flow meter, no ground would cause it to not function also. Machine really doesn't give a squat about utility company ground, just the ground plane on the board.
You can spend some time checking grounds back to the pin two connector. Poking the boiler with one probe and the other into the pin four hole will let you know if the boiler is ground referenced to the board.
As far as checking out the board, check the DC at the flow meter positive lug. You should see 18VDC or there about. Switch meter over to AC and see if you get a reading over a few millivolts. Two or more volts means cap is below rated capacitance. Not AC but meter sees rise and fall in voltage as AC. Which in our case is ripple. And not the infamous fortified stuff that competed with Boones Farm or MD2020.


#5: Post by jpboyt »

And if the flow meter is fed through the voltage regulator you would want to do preceding test for voltages between pin 1 and the ground lug of the 7805. Flow meters are most of the time fed unregulated DC but NS likes to use regulated on occasion which likes to heat up the regulator a bit. Your control box cover lists it as +12V so I am assuming it is not regulated.

LoudonMiller (original poster)

#6: Post by LoudonMiller (original poster) »

I was a mad dog guy!

Progress: I can get the pump to stop by grounding pin 4 directly to the body!

Problem: I've jumpered and snipped so many ground wires, trying different permutations to find the weak link that I can't remember how it should go!?! Smelled a faint whiff of motor smoke on the last try...

So how should my grounding circuit go?

120 outlet to ??? (I connected it directly to the motor ground...I don't think this is correct...)

Boiler body, to flow meter and pin 2. I think this is ok.


Team HB

#7: Post by JRising »

LoudonMiller wrote: Anyone have a thread on converting something like this to a manual operation machine?
Does it have a sight-glass already, or what do you mean by "Manual operation"?


#8: Post by WWWired »

Hi LoudonMiller :)

Fantastic post that is going to be a huge assist to many in future! Already some fantastic replies with some great fault source narrowing :)

jpboyt's posts are always pure brilliance and every word provides amazing insight. You have three of the absolute best here with BaristaBoy E61, jpboyt and JRising on the case haha! Awesome!!

I think Paul Pratt has some pictures of a Mac V that might show some of the wiring in the machine?