Gaggia TS Not Heating – Controller or Pressure Switch Fault?

If you have a Gaggia TS which is only intermittently heating the water in the boiler, this is most often caused by a faulty relay in the controller.

The main other causes could be a pressure switch fault.  Less likely are intermittent wiring fault, intermittent heater fault or intermittent contact of the over-temperature thermostat.  These latter causes are far more likely to cause a complete failure.

This section shows tests to determine where the fault lies.  You will need to be competent working inside live equipment to carry out these tests.  If you are not, then replace the pressure switch, see if that cures the problem, then replace the controller.

Test 1.  Confirm good measurement reference point.

We need to find an easy to identify reference point for our measurements.  One of the connections to the solenoid on the group head has three wire connections, this will be our reference.  With the red probe, we should measure about 230V AC on the live side of the group head heater thermostat (the side NOT connected to the group head heater).

Test 2.  Check the Controller Output

Whenever the coffee machine is on, there is water in the tank, and there is water in the boiler, as measured by the controller, relay K3 inside the controller should close and provide volts tot he pressure switch.

Measure the voltage on the pressure switch microswitch terminal which connects to the controller.  There should be 230V AC here for the heater to work.  If you don’t see 230V, then check:

1. Water in the tank and so the red tank empty lamp will be out.

If the lamp is lit, but the tank has water in it, check the wiring of the two probes.

2. Sufficient water in the boiler (if the boiler was emptied for transit, then you may need to power the machine up several times to fully fill the boiler).

3. Boiler probe clean of scale.  Remove the probe wire and touch it directly on the boiler.  The controller will think the boiler is full and power up the heater.  You should be able to hear the relay click.

4. None of the above.  Very likely a controller fault (but read to the end of this page).

Test 3. Test the Pressure Switch

If you DO see 230V on the pressure switch, then you should also see 230V on the side of the pressure switch connected to the boiler.

If this is not the case, then the pressure switch is faulty.


Test 4 The Overtemperature Thermostat

Move your red probe to the live side of the group head heater thermostat, and check both sides of the overheat thermostat.  You should see 230V.

If you only see volts on one side, the thermostat is open.  You may be able to reset it by pressing its reset button.

Final Notes

If it appears there are volts at the pressure switch output, and the overheat thermostat is closed, then the element is at fault.

We stock controllers, pressure switches, and heaters, so if we can be of any assistance, check our shop, theBottomlessCoffeeShop.

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24 Responses to Gaggia TS Not Heating – Controller or Pressure Switch Fault?

  1. Michael McNulty says:

    Hello Steven.
    In need of help with gaggia td………..
    I am restoring a machine i recently obtained.
    It was received untested, and with no history of maintenance or repairs.
    I removed the boiler and element and descaled both. Thoroughly scaled up.
    I had the element checked and was told it was fine.

    After cleaning and refitting, the moment of truth arrived. I connected to the water and Mains and turned the switch….. Heard a relay click in, then the RCD tripped!!!!!!!!!!!!
    Traced to pump stuck…… Freed off and refitted…… Turned switch and pump started running!!!!!!
    Then element started getting hot…… VERY hot…….. Switched everything off and manually filled with water.
    Machine now working OK….. Pressure gauges not reading, so swapped them and tried again.
    RCD tripped again……. Traced to now faulty element…..

    I thought the element was controlled by the pressure switch, which is controlled by the boiler level switch/element ……… Could you please advise how I check level so and pressure switch?

    Luckily, I have a donor machine so I can swap the elements over for testing…..

    Do you have a wiring diagram for a TD?

    And can you obtain spare parts?

    Sorry for the long winded post, but I didn’t want to leave anything important out….

    Thanks in advance for looking and any help!


  2. Michael McNulty says:

    That’s a bit expensive me thinks…….. But I will watch it with interest……. Might be worth refurbing the other one………

  3. Michael McNulty says:

    This is like the one I am refurbing

    I am having it resprayed, probably in metallic red.

    The other one is similar, but in stainless steel………

    Wonder how much it would fetch

  4. Michael McNulty says:

    Yes, that’s what it looks like.
    I will remove and measure tomorrow and note any relevant numbers etc

    The “diffuser” is the brass piece that screws to group head and shower screen screws on to.
    (Well that’s what someone else called it!)

    I will also measure the level glass.

    Do you sell silicon grease?

    Thanks again for ALL your help.

  5. Michael McNulty says:

    Hi Steven.
    Took out element today. There a 3 elements. The longest one is 2 15mm long, the middle one is 212mm and the shortest one is 195mm.
    Engraved on the flange is

    Firem 10/94

    V220 W2500

    V240 W2975

    Hope this helps with I’d.

    Level glass is 55x11mm

    Also need 3 tap washers.

    How do I arrange payment?

    Thanks again for all your help.

  6. Michael McNulty says:

    Hi Steven.
    Wondering if you received my comments….

  7. Nick Wright says:

    God morning. On an unrelated topic, I have a used TS that is in need of some repairs and while I am doing those (using your very helpful website) I would like to get the case powder coated. It looks like the case is held together with brass rivets – is this correct? If so I assume the only way of dismantling is to drill them out?
    The next question is where to get replacement rivets once the panels are re-coated. Any help much appreciated.

    • admin says:

      Hi Nick,

      I am sorry I have no idea about this, as I have not disassembled my machine.

      Please let us know how you get on and I would love to have some pictures to show others how to take the machine apart.

      The rivets should be easy to obtain (ebay, etc), but nut and bolt would be fine, and allow subsequent dis-assembly if necessary.


  8. Nick Wright says:

    Thanks Steve, good idea re: bolting together. I am taking a load of photos to help me reassemble and will share them assuming the powder coating goes to plan!

  9. Jules says:


    I have a Gaggia TS which is not working, it started leaking from the hot water tap and then just stopped working altogether. When I switch it on its making no attempt to heat up the water or pressurise.

    I am in Derbyshire UK and have been trying unsuccessfully to find someone to come out and repair it

    • admin says:

      Hi Jules,

      I am sorry I don’t know any repairers. It is a semi commercial machine, so any maintenance companies for machines in coffee shops should be able to help.

      Assuming the rear tank is full, and you have turned it off an on again (it can lockout if the water tank runs dry) then it is most likely a faulty pump, or controller. If you can hear the pump running, then it could be the element or the overheat thermostat inside could have tripped.


  10. Marijan says:

    Hi Steven

    I am posting a reply to this entry as I couldn’t figure out how to get in touch with you directly.

    As you seem to be one of the only people on the internet who seem knowledgeable about the Gaggia TS I was wondering if you could share a few thoughts on the following:

    I’ve been offered a showroom demo model of the Gaggia TS for a relatively good price by a Gaggia dealer (a new model would be way above my budget). I was wondering if you have any thoughts on how to check that the machine is working properly and that there are no ‘hidden’ defects which even a non-technical person like me could test for?

    The machine would come with a 1 year warranty and the dealer has his own workshop so there is some peace of mind, but would appreciate any thoughts you have.

    Many thanks,


    • admin says:

      I suggest you download the manual and read through it.

      That will tell you how it should work, or get the shop to demonstrate it to you.


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