I just took delivery of an old S20 Midi (2 group). The previous owner stated that one of the group headers doesn't work but I'm having trouble starting it altogether. It's plumbed in for water supply and the drain is currently to a bucket. To start the machine, I do the following:

Turn the power knob from the center (off) position to the left (1) position. This fills the boiler. Autofill starts, then stops some time later. I then switch the machine to the right position (2). This allows the heater to start and throughout this, it's clear the temperature goes up in the boiler and the pressure gauge goes up too. While the pressure is below 0.5 bar (in the yellow zone), I can operate both group headers using the brew override buttons, providing a good sprinkling of water (no PF's on). However, once the pressure gets into the green operating range, the brew override buttons both flash green simultaneously at about one flash per second. The boiler goes until pressure reaches 1.1 bar then turns off. The pressure falls progressively to 0.9 bars, at which point the boiler kicks in again and then starts the heat cycle again (heating last about 30 seconds). This continues endlessly. I had the machine on for about 30 minutes and it just continues to cycle. Regardless of what group header I'm trying to use I can't get it to brew or get any of the buttons to operate anything. I can operate the steam wand successfully and the hot water wand as well in both the yellow low pressure zone and in the troublesome green zone.

Any advice would really be appreciated. I'm sorry if it's a really simple thing I'm missing but this is my first commercial machine and I want to try and make a go of getting it to work. After ascertaining it's condition I plan of a rebuild but for now I want to get a good idea of what I'm starting with.

Congratulation for your machine.
If you have just filled the whole boiler, it could take some time for the temperature to stabilize, especially if you have entered fresh cold water into the boiler. You seem to be in Calgary and I suspect the 'fresh' water to be quite cold at this time of the year. You should not have 'blind faith' on pressure gauges, especially on older machines. Is it a single or double pressure gauge? One would be for the boiler and the other should be for the motor/pump pressure.
The next thing is, are the groups clean? They may be very dirty and clog with coffee oil. Remove both dispersion screens and take a good look at them, if they are dirty, clean them with a coffee cleaner. If they are dirty and no water or very little water passes true, the electronic card on the left side will detect it and the touch pads will start blinking indicating a problem. The wires to the touch pads and flowmeter are very cheap and do not resist heat very well, they have a tendency to dry up and crack quite easily. Check for broken or crack wires, especially those that goes to the two flowmeter as they are near the group head. Do not remove or change any before you take pictures, a lot of pictures. There is a plus and a minus on the flowmeter, make sure if you change the wires that they are reconnected in the same way. Make sure you have pull the electric plug out before playing around with the wires. The pipes may also be full of scale preventing a proper flow.
I know this machine, so if you need some help, let me know. They are decent machines, easy to disassemble, descale and reassemble. One or two days work.

Thanks for the reply Alain, definitely appreciated. I removed the group screens, the right one was very dirty. However, no luck improving the operation. I have some pictures though which may help. First, I actually can't get either group to flow using the manual brew buttons anymore, and no other buttons work either. As before, the steam and hot water wands work well, but these are both manual valves. As per the pictures below, the hot water is not a button operation, it's actually on a manual valve which looks identical to the steam (though it flows water mostly (not much steam). If you recall from the first post, the group headers used to flow at low pressure with the manual brew buttons but now I don't get any flow. I did go through the wiring. Although some is dirty, none is really damaged. The two suspicious things are as follows:

1: random wiring harness unconnected at the front of the machine:


2: random (solenoid valve?) also hanging loose. This is wired along a similar loop as the boiler fill solenoid in the background:


Another view of the loose item:


A view of the inside of the hot water wand: note it doesn't look like a backyard modification, the frame is nicely cut out so it looks original. My first thought was that the loose gear was from an old button-operated setup replaced by a mechanical valve but i'm not sure about this anymore:


Finally, a view of the front. Nothing much to see here, just how the hot water wand is done (just like the steam which is on the left).


So that's about all for now. I apologize that I haven't looked at the rancilio parts manual and determined what it is I'm missing but that's my next step. I need to find out where that wiring was taken from (no obvious missing links) and more importantly where the yellow box goes and what it is...

Thanks for looking, I definitely appreciate any and all comments, I'd be very glad to get any advice and pointers...

All right, We are getting there slowly. Your picture number one, is low voltage and is intended to go to the water push button, which you do not seem to have on your machine, leave it alone. On your machine, you should have 3 of these small square boxes, one is the solenoid valve water feeding which seems to be there and working, then you should have 2 more of those, one per group, they are groups solenoid valves. If I may suggest, leave you machine unplug. The solenoid valves operates on 220volt and if they are loose, there might be a fire hazard or/and you could burn your main electronic board $$$$. Remove the front panel, where the lights are and on/off button (there is a small screw to unscrew at the bottom of the on/off button) once remove take a picture and post it, you should see the two solenoid valves attach to the group. I suspect your group head and machine boiler/pipes to be very dirty, of coffee residue and of scale. Be safe and patient, leave it unplug for now.

Definitely appreciate the response. I took the front plate off as suggested to find two solenoids in place. One is a Parker, the other a Sirai, so I'm guessing one has been replaced in it's lifetime at least. I decided that for testing purposes, I'll clean up only one of the group headers (the right one) so I disassembled the group and am cleaning out that header now. I will put it back on and see if I have any changes. From first inspection, the group I removed is definitely dirty but not that bad. I did a little flow test and it doesn't seem plugged but we'll see what the cleaning accomplishes. Here are some photos of the groups:

First, the right group which is now being cleaned:


The left group (note the valve here is a parker, the right valve is a Sirai, so one might have been replaced):



Finally, the front with cover off:


I'll post an update on the cleaning status and any results. I also tried to get in touch with the last owner for some info but we'll see how much that helps.

One troublesome thing is that because I've got both group solenoids, and one for the tank, I still have an extra solenoid floating around. Could this be a leftover from an economizer? the Midi Tecnas have an economiser solenoid. I'm mad at myself now, I left my parts diagrams on another computer so I'll be checking those out carefully on Monday. One other thing, Alain, I think you were right, the extra wiring harness was probably a factory deal and meant to stay closed. The solenoid valve was just taped over with electrical tape but the wiring harness actually had heat shrink tubing over it so it leads me to think it may have been a factory job.

As before, any and all insight is definitely appreciated, thanks for reading.

Just an update. I think the extra solenoid is from my leftover water wand. The harness too. From looking at the inside of the frame, the round hole for the valve was cut nicely, but isn't the same as the stamped hole for the steam valve. Someone in replaced the button for a valve, not sure why. Perhaps the valve broke down but regardless, I don't have the old parts to put it back together as it was. I'm cleaning one group header now so we'll see if it helps.

Hi again, you are right, I could understand the extra Wiring Harness, but not the extra solenoid, which strongly suggest that this machine previously had a push/button for the hot water. I took a look at Rancilio pictures of the machine you have, and the push button is where your water knob is, someone made a change to the machine in order to eliminate the solenoid hot water valve.
Try to undo both groups, they are easy to take apart, remove all screws and clean the groups with a coffee cleaner. If you see scale, you are going to have to use citric acid, but use a coffee cleaner first. Take pictures! I am sending you a part diagram of your machine. You could also take a look at your electronic card to see if there aren't broken fuses. (unplug your machine first)

Thanks for the picture Alain, I have the same on another computer, not with me this weekend unfortunately. I cleaned out only the right group header. It was disconnected from the piping and frame, stripped of the solenoid, separated out and cleaned. I haven't gotten around to getting any real citric acid but I can see it's a must now. I boiled the group header, screen and various screws in concentrated lemon juice and water for a number of hours. As a result it gave up quite a bit of coffee grime and mineral deposits but it's not perfect, so when I get some citric acid I'll redo this with the rest of the machine.

After bolting it back up, I had some positive results. There is a very small orange LED on top of the Gicars which rest above the group headers. When on the "pump only" power setting, both LED's are off, and I can operate the manual brew button on both groups (the respective LED starts to flash). On the right (clean) group, I can also operate all the dosing buttons, which is nice. When these operate, the respective orange LED also flashes until done. I can also interrupt the dosing with the manual brew button. I think this is generally how it's supposed to function all the time. To summarize, no dosing on the left group but it's dirty so that's my project for the day. As for the "Pump and Heater" power setting, I can do all of the same functions on the right group header as previously described when I initially switch to this setting, but when the pressure/heat start to build, this group header also stops operating, as with the left group header.

I think my next course of action will be to clean the left group header, and I may venture and clean our some piping too, almost more so to see how dirty things are inside. Aside from the group headers, can anyone suggest the most plugging/buildup prone parts to clean? I definitely plan on a rebuild but I want to really ascertain the condition of the machine as much as possible before I take it apart fully. Not that the pictures previously posted are complete but the bottom of the frame has some rust and lots and lots of coffee junk on it. The machine arrived with the cup holding tray but is missing the tray that sits below it so there's been lots of dropping of random junk onto the boiler and internals so the cleaning will be needed. I'll do a quick paint job on the frame too.

Alain, as before, thanks for the advice, definitely appreciated.

Hi, There are two hydrolic 'path' in most espresso machine, one is for the boiler and the other one is for the heat exchanger/group. Follow the pipes from the two groups, undo all of them, clean them and put them back. You will also meet two strange beast on this path, they are 'flowmeter', the small rectangular metal boxes over the two groups head, they may be clog with scale. Becarefull when you undo them, take pictures of the electrical wiring , which color goes to - and which one goes to +, you do not have to undo the ground wires. Be carefull and patient when removing them, sometimes it is difficult to undo the pipes, try not to bend any pipes, in fact don't try, just don't bend any pipes. I have seen people bend whole boiler, so imagine pipes. When you will remove some of the pipes that attach to the lower part of the boiler, water will come out, this water may be quite hot if the machine was not cold dow before. You could also open the flowmeter by removing the 3 or 4 screws on the top, in which case you might have to change the O'ring. The interior of the flowmeter is ususally clean, even in very dirty machine for a unknown reason, but the holes are sometimes full of scale, particularily where the water comes in, where the hole is much smaller, about 1/16 inche. If there are clog, try to insert a neddle to unclog them. If these pipes have scale, be sure of one thing, the whole machine has scale. I have seen boilers which were half full of scale.

Hi Alain, thanks for the good advice. I actually took the initiative last night and rebuilt both Gicar meters. They were both very dirty inside, with mineral deposits around the curcumference of the meter body. I also took the time to clean the integrated filters on these and ensured that both the inlet and discharge were clear. To remove the scale deposits, I used fine sandpaper around the inside of the body and on the bottom of the body as well as on the cover. As a result the rotors now turn well inside the body. I also cleaned out all the boiler-to-group piping and all the piping between the boiler and Gicars, as well as the other Gicar piping between the supply(?) and the flowmeters. I took advantage of the two group setup and only cleaned one group at a time, ensuring I had a good template for reconnection when doing the other group. I'll give the machine another test tomorrow night but the more work I do on it the better I feel about a rebuild and the more I see the need for it. I'll definitely post the results of my test...