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.
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.