Gaggia Classic Wiring Diagrams

Gaggia Classic Wiring Diagram

When you switch on the power using the main switch on the front panel, power is provided to the front panel neon, which lights provided the thermal fuse in the neutral wire is intact.

Power is also provided to the elements, via the coffee thermostat and the steam thermostat.  If either of these has dirty contacts, then they may not provide power to the element, and so it will not heat the water.  You may notice the water not heating quickly as the thermostat contacts dirty and create resistance to the current reaching the element.  This will only get worse until the thermostats ultimately fail.

 

 

 
Gaggia Classic Wiring Diagram

When the water in the boiler has reached 95degC, the coffee thermostat will open (4 in the diagram above).  The current which was heating the element will now take the alternative route through the neon (11), which has a high resistance, and although in series with the element, will not allow it to continue to heat the water.

Of course if the boiler cools down, the coffee thermostat will close and the cycle will continue.  If the coffee thermostat is faulty and the contacts have welded themselves together, then the coffee thermostat will remain closed and heating will continue until the steam thermostat (5) opens and the neon comes on.  When a coffee shot is subsequently drawn, steam will come out, rather than hot water.

 

 

 

 
Gaggia Classic Wiring Diagram

The coffee switch (9) is closed to pull a shot.  This provides power to the pump (10) and the 3-way solenoid (8).  The three way solenoid routes the coffee from the boiler to the coffee (it normally sits idle and routes the coffee water to the drain, to release pressure from the puck).

 

 

 
Gaggia Classic Wiring Diagram

To heat the water to make steam, the steam switch (7) is closed.

This shorts across the 95degC thermostat and so the steam thermostat (5) now controls the boiler temperature.

It also opens the power feed to the solenoid (8), in case the coffee switch has accidentally been left closed, or the coffee switch is operated (otherwise steam would issue from the group head).

 

 

 
Gaggia Classic Wiring Diagram

When the seam in the boiler is up to temperature (145degC) the steam thermostat (5) opens, and the neon (11) lights again.  You can now steam milk.

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19 Responses to Gaggia Classic Wiring Diagrams

  1. Jesper says:

    Hi! I Just broke my main switch and thinking of replacing in with a own made board with regular switches. Do you what voltage the lights are using?

    • admin says:

      In Europe, the neon in the switch is for 230V AC.

      The switch is a standard size, so could be replaced with a similar one easily until you make your modified board.

      Steve.

  2. Jesper says:

    Thanks a lot for the super fast reply!!

  3. Charles Pitman says:

    I had to deconstruct my machine to replace the temperature probe and associated switch. I labeled every dang wire except two … the ones that attach to the 11o volt receptacle. I have a blue wire and a violet (brown?) wire and don’t know which one goes to which prong. I know that one is neutral but which one and one line, but which one is which?

  4. Charles Pitman says:

    I just answered my own question. Blue is neutral according to the wiring diagram helpfully appended on your web site. I couldn’t read it at first, but found a way.

  5. Malcolm says:

    Why does the “ready” light provide enough resistance to keep current from flowing through it but not the “on” light?

    • admin says:

      The “Ready” light is lit due the the current flowing through it and through the heater resistance.

      As the lamp is a much higher resistance than the heater, the heater stops heating the water, until the hot water thermostat closes, and shorts out the “Ready” light.

      Both the On and Ready lamps are much higher resistance compared to the element.

      Steve.

    • erwin ignacio says:

      ready light is in series with heating element and will provide resistance when the coffee thermostat opens. ready light is on the path of heater.
      while the “on” light is parallel with the heater. on light is not on the path of heater.

  6. admin says:

    I think that is what the words say.

  7. Ed says:

    Hi Great wiring diagrams and that you for the parts. My fault was the machine started to intermittently turn the water pump on when I first switched the machine on for a few days. The machine then did not turn on at all. So, I followed the blog and diagrams and ordered some spares anyway. What had happened was, the safety thermal cut out switch had triggered due to overheating and I reset that and the machine worked for a while and then the safety switch tripped again. So I cleaned the “Boiler Level Probe” and then put all back together. However, steam started to come out of everywhere after a while, so I turned it off and re-checked, this happened twice then issue was the depth that the “Boiler Level Probe” was inserted to the boiler, which has an impact on the water level and therefore the pressure. All is now well and I have the parts from Stephen ready for the next exciting adventure with my Gaggia.

  8. Chris says:

    Good stuff. I wonder if you might be able to help me with the following: I’d like to add an intermittent relay that would turn on the heater about 40% of the time while brewing. (Others have estimated that to be about the right amount). The idea is to add just enough heat to the cold water coming into the boiler to get a consistent brew temperature. I realize that a PID can do this, but a relay is much cheaper (and can be hidden inside the machine). Can you think of a way that I can add a relay so that it will neither damage the machine nor screw up the current button functions (steam/steam+brew)?

  9. Wezi says:

    Hi, you may be my only hope! Today, when dismantling the Gaggia Classic to get to the internal boiler the switches in the main housing sprung out leaving behind a mess of springs and switches. Now, I can piece everything back together, but one piece has left me puzzled as to here it goes, it looks like a fuse, miniature in size, approx 3-4 millimetres in length and 1 mm wide

  10. Mohammed says:

    Excellent article. One question, where in the circuit would the resister sit for the ON and READY lights. After re-assembling the light switch due to a break with the bezel i’m left with a component which resembles a half way house between a 4mm fuse and a resistor.

    • Mohammed says:

      Hi, in answer to my own question the small piece is a resister, sits against the circuit and is connected to the light via a small spring (not the springs used to pivot the switches). If it wasn’t for this page explaining the circuitry I wouldn’t have been confident enough to have opened the switch a second time to make the fix. thank you

  11. Kumar says:

    Hi all,

    So just got one of these babies only to find out it’s not working, the only thing that happens when plugged in is the main power switch and the water light flicker on and off really quick besides that nothing happens. I’ve tracing all the wires and everything so far seems right. Any ideas?

    • admin says:

      I would try a new mains lead. It sounds like a poor connection somewhere between the wall outlet and the mains switch.

      Steve.

      • Kumar says:

        So I checked the power and it has power energizing throught and sorry if this is in th wrong area this is regarding a TS not classic

        • admin says:

          This is the place for the TS !

          If the mains power switch neon is flickering, the problem must be prior the switch, ie the mains lead or power input connector wiring to the mains switch.

          Steve.

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