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Gaggia Classic - electrical issue

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  • Gaggia Classic - electrical issue

    Hi all,

    I have a Gaggia Classic that's around 7.5years old. The first couple years I didn't understand how capable the machine was nor what I was doing - and did very little maintenance! Thankfully after a couple years (and a visit to CS) I started taking better care of it.

    First some background:
    Despite backflushing regularly and descaling once a month the output from the group head was reduced to a trickle. Given the age of the machine I followed the instructions here (Espresso Mods | [protofusion]) to have a look at the condition of the boiler.

    There was some pretty extensive scale buildup inside, along with some corrosion - there was a smile pile of aluminium chips at the bottom of the boiler when I cracked it open.

    Anyway, after a soak in descaling solution and some work with a brass brush and dremel tool the inside of the boiler was looking a lot better. I put in a new boiler gasket along with new group head gasket and proceeded to put the machine back together.

    Now to the issue: With the machine fully assembled; when I switch it on it trips the house circuit breaker.
    At first I thought maybe I had gotten some moisture into the heating elements, however checking with a multimeter shows there is no short in either element.

    If I disconnect one of the wires in the heating element circuit (the wire connected to the 145deg thermostat, or the heating element on the side between the boiler and the steam wand) then the machine can successfully pump water through either the group head or the steaming wand.

    Yesterday I spent a couple hours checking the switch connections and they all seem fine. Similarly the pump and the solenoid both seem to be working okay once the heating circuit is disconnected.

    I took photos and labelled all connections before taking the machine apart and all the wire connectors are back in their original places.

    Any suggestions as to what could be causing the machine to trip the circuit breaker? Has anyone seen anything like this before?

  • #2
    What is the resistance across each of your heating elements?

    Despite what you say, my money is on you mixing up the heating element connections and shorting 240V across the boiler housing. *EDIT* Actually, they're not MIMS elements so they shouldn't be able to short out like that, but try this anyway and let me know what happens)

    I would suggest removing all the element connectors and running the machine again. If it doesn't trip and you're confident in your ability to not fry yourself, test for voltage (250V+ AC range) between each of the four connectors (the ones that press onto the electrode pins on the elements.

    Mark two that register ~230V between them, turn the power off then connect them to one of the heating elements (they're external U-shaped things, should be easy to see which ones are on the same heating element). Then turn the power on. If it doesn't trip, power off, connect the other two to the other element and turn that on.


    • #3
      Thanks for the reply Dragunov21. I was borrowing the multimeter off my dad so I'll need to grab it again to test what you've suggested.

      FYI I did grab the Gaggia Classic wiring diagram (220V) from the Gaggia Yahoo Group (attached here) and spent quite a while confirming that it matched.

      Based on the diagram, if I disconnected the top right element electrode pin (the top right of the four pins labelled '6') OR the connector on the right of the 145deg thermostat (on the right of label '5' in the diag) then the machine would turn on and pump water successfully. Obviously it wasn't heating up since the elements were disconnected.

      If both of those connectors were in place then the short occurred. There was no resistance across the 145deg thermostat (label 5) - I'm figuring that's normal since you need a circuit to begin heating the element and then the switch opens once it gets up to temp. Is that right or have I got it backwards?
      Attached Files


      • #4
        Weird; that doesn't quite match up with the innards of my Classic; mine doesn't have what appears to be a thermal fuse, marked 3.

        Additionally, it looks as though the 220V version is supposed to have the two elements connected in series, with power applied to the top-left and top-right terminals of the diagram and a jumper connecting the bottom-left and bottom-right terminals. I'd have to open mine up to have a look but that doesn't seem to match mine...

        Are you able to trace your wires and confirm that you have a lead connecting one end of one element to one end of the other?

        I'm gonna have to check the current draw on mine to make sure mine isn't wired to run on 110V >_>


        • #5
          That wiring diagram is consistent with how my classic is wired.

          One option is to make a small patch wire using insulated spade connectors to connect both the wires that go onto the steam thermostat.
          If the machine does not trip then go by yourself a new steam thermostat.

          You can do the same with the brew thermostat as well. In both circumstances make sure the machine is full of water and you are running the brew switch otherwise it will overheat within minutes and fry the element or blow the thermal fuse.

          Does not take much to trip a RCD, i would be checking your all of your connections are sound, be sure some moisture has not go into one of the insulated connectors or something like that.

          An example one of the classics i bought for a family. member, after heating up fine ect, only while pulling a shot would it trip the RCD.
          Under pressure the pump was spurting out a very small amount of water onto some of the wires.

          Where in sydney are you?


          • #6
            The elements should not be damaged by running a dry boiler (even without steam t-stat) as they are externally-mounted and protected by the thermal fuse, though you're right about the thermal fuse blowing.

            A thermostat fault should not cause this issue unless the housing had been physically damaged as they are a short circuit that breaks once temp is reached.

            It's a good point about the RCDs, though once again if the difference between tripping and not is a disconnection of the heating element circuit, I'd suspect that not to be the case as long as the insides of the machine aren't covered in water.


            • #7
              Dragunov21 - I can confirm that my machine is wired up per the diagram with the bottom left and right terminals connected to one another, putting the heating elements in series. I can also confirm that there is a thermal fuse (it's covered by a rubber sleeve) and that the fuse is still intact.

              Steve82 - we tested the top thermostat and there is a circuit, which matches the behaviour that Dragunov21 mentioned just above. I'm based in Carlingford.

              The whole interior of the machine is dry - I have attached a picture of the current state. You'll notice the numbers on the connections that I marked before I pulled any of the connectors off. The machine was tripping the circuit breaker before any water got pumped in, it was only by disconnecting the heating elements that I could confirm the pump/solenoid was functional.

              As I said, we spent a couple hours testing various suspects but everything seemed to come up fine - and is the reason why I'm stumped.
              Attached Files


              • #8
                Interesting all sounds looks good.

                I was going to offer a lend of a known working boiler in my spare parts machine, but i am on Nth beaches mona vale way, bit of a trek.
                I sometimes go up up Hornsby way though if you dont get it sorted.

                The only other thing i can think of is that there is a small crack in the ceramic insulation of that element on the right side, possibly from dropping or knocking? or contrary to what Dragunov believes, can happen by overheating / constantly heating a dry boiler,like what can happen often after people dont prime / run a cooling flush after steaming.


                • #9
                  to blow a breaker but not damage anything inside the machine seems like an active to neutral short to me. i've done it recently on the steam element inside a delonghi auto machine.
                  the previous owner had tried to replace the whole element assembly (whereas the only problem was an open thermal fuse, sigh -.-) and had connected active to neutral across a thermal fuse. not sure how someone who called themselves an electrician managed that but whatever. what happened when i turned it on (i hadn't checked the wiring) was that as soon as it completed it's start up check and initiated heating, the breaker blew.

                  if you have a shorted element or an active or neutral to ground short, the response when turned on will be different. the machine case will go live and you could damage the internals of the machine.
                  as you have said, you've wired everything up ok so that can't be the issue, what i'd be looking for is possible shorts between wiring. you may have accidentally squeezed some wires between metal and broken the insulation perhaps, or something similar. cable ties are surprisingly sharp on the edges so if one was over tightened at a point of weak wire insulation it could have broken through. pretty slim chance of that actually happening but you never know.

                  looking at your photo, there is some noticeable kinks in the brown wire (active) and the blue wires (some would be neutral) have limited flexibility due to the spade connector insulation and placement. you have a multimeter there so set it on the lowest ohms scale and measure between active and neutral connections anywhere on the machine. if you get a reading at any point, check any related wiring near that point for damage.


                  • #10
                    Originally posted by Steve82 View Post
                    contrary to what Dragunov believes, can happen by overheating / constantly heating a dry boiler,like what can happen often after people dont prime / run a cooling flush after steaming.
                    Apologies if I'm mistaken, I just didn't think it could happen with the elements connected to a heavy boiler housing with a thermofuse.


                    • #11
                      Thanks for all the ideas everyone.

                      Looks like some more time testing the wiring with the multimeter is in order.

                      I'll let you know how it goes.


                      • #12
                        Just a quick update - measured the resistance across each of the elements: LHS element 21.6 ohms. RHS element 21.3 ohms.

                        None of the pins are shorting to to the boiler (or even the outer casing of the heating elements).

                        Both thermostats are currently closed and the thermofuse is intact.

                        Tomorrow is a new day, and I'll start tackling the wiring and connectors.


                        • #13
                          When you say none of the pins are shorting to the boiler/element sheath, what resistance values are you getting? Complete open circuit/>1MOhm?

                          That's really really weird, wish I could drop by and have a looksie myself, but I'm a bit far away...


                          • #14
                            Hey Dragunov21 - yep complete open circuit from the boiler to any of the 4 pins.

                            I've had a look over all the connectors and they are all intact and clean without any loose wires. Similarly cannot find any damage to the wiring insulation.

                            Not sure if this means anything yet (it's a bit early) but when I disconnect everything from the front switch plate except the 3 poles on the main power switch it still throws the circuit breaker when switched on.

                            Just to be extra sure I disconnected the pump and the solenoid and it still threw the circuit breaker so that confirms it's somewhere in the heating circuit.

                            Genuinely stumped.


                            • #15
                              Originally posted by esmondw View Post
                              Genuinely stumped.
                              G'day esmondw, PM Sent.