erics wrote:Yes - The brew pressure gage is reading brew boiler pressure so I would loosen one of the connections at either end of the gage and take a reading then.

or simply open up the bleed screw in the group a little bit, then drain the boiler through the expansion valve.

ken

erics wrote:Yes - The brew pressure gage is reading brew boiler pressure so I would loosen one of the connections at either end of the gage and take a reading then.

Of course, Eric means for you to turn off the machine, let it cool down, and drain the brew boiler before you disconnect anything.

Disconnecting the tube at the gauge end might be a good test for a vapor lock or some sort of flexible blockage in the tube, but unfortunately the tube can't be disconnected at that end. It's soldered to the gauge.

I'm not sure there's any value in disconnecting the tube at the boiler end beyond what you would see if you simply drain the boiler. You might be able to see and clear a blockage at the very end of the tube, but if it's further down the tube you won't be able to see it and won't be able to clear it.

Given that the tube is soldered to the gauge, a blocked tube pretty-much requires replacing the entire assembly.

Again, my understanding is that the kind of failure you're seeing is pretty common with this type of gauge. When I get around to it, I'll disassemble the defective gauge I took out of my GS/3 and see if I can determine what caused it to fail.

OK, I took the gauge apart. Here's what it looks like inside:



I sawed off the brass threaded coupling to which the tube from the brew boiler is soldered, and cut down the rectangular brass block behind the coupling as much as I could. Essentially, the tube from the brew boiler is connected to the small hole you see in the front of the rectangular brass block. Incoming pressure turns the tiny cylindrical gear directly under the hole (the one with the watch spring at the bottom.) The gauge pointer is attached to the axle of the cylindrical gear. As incoming pressure turns the gear, the pointer moves clockwise and the spring tightens. The cylindrical gear meshes with the partial gear to the right, which in turn is connected to the lever mechanism at the far right. The lever pushes against the large semicircular metal strip bent around the circumferance of the gauge (ignore the gash in the left side of the strip -- that happened when I sawed off the rectangular brass block.) The strip resists the movement of the lever, and in turn the gear and pointer, thus determining the sensitivity of the gauge. The more you want the pointer to move, the more you have to press against the strip (i.e., the greater the incoming pressure has to be.) As pressure is removed from the strip, it pushes on the lever, which moves the partial gear and cylindrical gear back in the other direction, and the pointer towards zero. With no pressure on the strip, the pointer should be at zero. I'm not sure, but I think the role of the tiny spring at the bottom of the cylindrical gear is to ensure that the pointer returns all the way to zero. There's a tad of slop in the lever mechanism and I think the spring is there to compensate for it.

I believe the most likely explanation is that the tiny spring has "relaxed" and isn't pulling the pointer all the way to zero. It's either that, or the metal strip has relaxed and isn't pushing back on the gear all the way. In either case, the failure was in the mechanism, not the tube.

Many thanks for the detailed replies. And an extra thanks to Dick for going above and beyond investigating the cause of the failure.

I traded emails with Chris Nachtrieb and I need to put a call in to Roger (service manager).

I have a slight concern is that I might needlessly be replacing my pressure gauge. For GS/3s in pour over mode, is it true that the brew pressure gauge should read zero after some period of time (as the steam boiler gauge does)?

BTW, I misread the Scace II pressure (which is hard to do because it has a giant, very nice pressure gauge, but the tick is every 5 psi, not 10). I'm actually seeing ~91 psi (6.3 bars) at the group head. Is there a consensus what it should read? If so, since I have the Scace, I could adjust now rather than wait for a new brew pressure gauge.

Cheers,
John

jakline wrote: Is there a consensus what it should read? If so, since I have the Scace, I could adjust now rather than wait for a new brew pressure gauge.

Cheers,
John

around 9 bar

jakline wrote:I have a slight concern is that I might needlessly be replacing my pressure gauge. For GS/3s in pour over mode, is it true that the brew pressure gauge should read zero after some period of time (as the steam boiler gauge does)?

BTW, I misread the Scace II pressure (which is hard to do because it has a giant, very nice pressure gauge, but the tick is every 5 psi, not 10). I'm actually seeing ~91 psi (6.3 bars) at the group head. Is there a consensus what it should read? If so, since I have the Scace, I could adjust now rather than wait for a new brew pressure gauge.

Yes, in pourover mode both gauges should go to zero when the machine cools down. When plumbed in and the brew boiler is full, the gauge will read the line pressure (usually 2-3 BAR depending on the external regulator setting.) You have to turn off the water to get the pointer to zero.

You can use the Scace II to set the pressure at the puck to 9 BAR (I have mine set for about 8.5 BAR.) That's what I did before the replacement gauge arrived. If the brew boiler gauge is working correctly, it'll read 1-2 BAR higher because the pressure drops across the gicleur (flow restictor) in the group head. Your probably-defective gauge will probably read more like 11-12 BAR when the pressure is set correctly with the Scace II.

Ken Fox was correct in that the easiest way to "check" the zero on the gage is by loosening the bleed screw on the grouphead as detailed in your owner's manual. Do this with the machine off and "cold".

Your Thermofilter II reading of 6.3 bar indicates to me that your machine was originally set up for plumb-in operation. Adjust the pump relief valve such that you get a 8.5 to 9.0 bar reading on the thermofilter gage and, for historical purposes , note the reading on the brew boiler pressure gage.

Ken Fox wrote:around 9 bar

Thanks. It seems some set it lower, but I'll go for 9.

Peppersass wrote:Yes, in pourover mode both gauges should go to zero...

Mine is in pourover mode. Time for that new gauge.

Peppersass wrote:You can use the Scace II to set the pressure at the puck to 9 BAR...

This the the nice part of this saga. I don't have to wait for the new gauge.

erics wrote:Your Thermofilter II reading of 6.3 bar indicates to me that your machine was originally set up for plumb-in operation.

No, *I* set it up to read 9 on the integrated brew pressure gauge. I also took a Scace II pressure reading that I am sure did not read 6.3 bar. Unfortunately, I didn't write down the reading.

What happened is that I lowered the pressure once or twice--when I saw the gauge reading high--to keep the integrated gauge at 9 bar. I thought nothing of it, since I read on one of these threads (probably the owners' thread on coffeegeek) that it was normal to have to do this when the pump is breaking in. Stupidly, I did not get out my Scace II before making the adjustment(s).

Again, thanks to all for your replies.

Cheers,
John

jakline wrote:What happened is that I lowered the pressure once or twice--when I saw the gauge reading high--to keep the integrated gauge at 9 bar.

If it makes you feel any better, that's exactly what I did. I failed to ask myself why the pressure needed adjusting, and for a long time failed to note that the pointer wasn't returning to zero when the boiler was drained. I happened to notice it by random chance.