Quick Mill QM67 Flow/Pump Help - Page 3

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Screamsi (original poster)

#21: Post by Screamsi (original poster) »

Update again.

So the issue came up again, no water from the group. Ran the pump for a good 40 seconds, and no brew pressure or water whatsoever. Shut off the brew valve, tried again and pressure did build the second time, albeit very slowly.

I hope replacing the solenoid valve corrects the issue.

- Ulises


#22: Post by Giampiero »

When the machine works, what is the max pressure you can reach using the blind filter?
Ah ok i saw your first video, anyway i don't want to change your idea, but in my humble opinion this is not an issue related to the steam boiler solenoid valve otherwise you should note a pressure modification ( depend by the leaking flow rate) in the steam boiler gauge if the valve is leaking into the steam boiler.
Moreover even if the valve is leaking into the steam boiler, you should anyway see some pressure value in the brewing pressure gauge.
Do you ever tried to check if the drain pipe inside the water reservoir it still to discharge water during a stand-by period, i mean more than the OPV could discharge normally?

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#23: Post by cafeIKE »

It always helps to know what occurred before the problem

It would be well to leave the covers off 'til this is solved so you can see what's happening:
  • is there return flow to the reservoir?
  • is the pump feed full of air?
  • how hot is the pump body?
  • is there a lot of air in the bleed tube?
  • pump feed crimped / twisted / kinked?
Was this the first shot after turn on?

If you run water out of the group before lock in, how long does it take for flow to begin?

Screamsi (original poster)

#24: Post by Screamsi (original poster) »

I'll keep the cover off to keep a closer eye on things when it happens again.

As far as that time, the machine pulled a shot successfully maybe 2 hours prior to it not pumping for the shot in the video. Pump lines are free of kinks and twists - I've tried to keep them as reasonably straight as possible.

It sounded almost like the pump was running with slightly lower voltage. When I tested after the issue, flow was pretty slow, and it picked up after running the pump for about 30 seconds. It was audibly "stronger" when flow picked up to normal. Didn't get a voltage reading because I was about to head off to work.

Do you think I may have an issue with the Gicar unit? I've checked all of the connectors and they all look to be in pretty good condition - nothing brittle.

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#25: Post by cafeIKE »

The Gicar typically controls the pump in parallel with the brew switch, so me thinks not.

If I was to try to simulate the behavior, I'd pinch the pump inlet. Hopefully the inlet has a filter screen or is cut with a V to preclude sealing against the reservoir.

I mark the tubes so I can ensure they are always correctly positioned

Screamsi (original poster)

#26: Post by Screamsi (original poster) »

I'll try that and report back. Inlet does have a filter on it, so I don't think it's possible for it to get stuck on one of the reservoir sides with it's own suction.

Screamsi (original poster)

#27: Post by Screamsi (original poster) »

Ok, so hopefully (knock on wood) I've finally found the problem.

tl;dr - It was the thermistor.

Ike, you were right!

So here's how I came (with help) to that conclusion. The day after my last post here, I called Chris Coffee to make sure I was ordering the correct solenoid valve. In speaking with their service department, I gave them a quick run-down of the issue with my machine. They mentioned a few of Ike's suggestions, and then asked if I had tried running the machine without the thermistor's thermal protection. They recommended I try that before ordering a pricey solenoid valve.

I mentioned that since the pump was new, I wasn't worried about the thermistor. It was then that I realized my mistake... new pumps don't come with thermistors! I didn't remember/realize that the whole time I had been using the one that came with the machine.

So I went ahead and removed the thermistor and pulled a couple of shots. Instantly, I noticed the bitterness and harshness from my coffee was gone. The pump sounded the same, but the taste was night and day better. Also, my pucks were not as wet as before. Fast forward 2 days and maybe 10-12 shots - no issues with water not coming out of the group.

I believe the original thermistor was on its last legs (burned out?) and was cutting the voltage slightly to the pump (for protection). That, in turn would cause my brew pressures to fluctuate and be inconsistent. Hence the bitterness in the coffee. Brew pressures were not fluctuating enough to be noticeable on the pressure gauge, so there was no way to tell. At times when the thermistor cut more voltage from the pump - that is when I would not get water coming out of the group.

Needless to say, I will be ordering a new thermistor for the machine.

Lessons have been learned through this entire process. Be methodical, and inspect all components. Even if you're 99% sure a part isn't the problem.

Thanks to everyone who contributed to the troubleshooting! I hope this prevents headaches for someone else in the future!



#28: Post by Pressino »

Thanks for the follow-up on your baffling problem, and Kudos to Ike for suggesting the diagnosis! Very clever!


#29: Post by Giampiero »

Great news, enjoy your coffee.