I get quite a few questions about the Gaggia TS operation, mainly why it does not heat up.
I thought it would be useful to look at the electrical operation of the TS in some detail.
The TS User manual (Google search for Gaggia TS Full Manual TS 03-08-04.pdf) contains a wiring diagram (with a wiring error error in the region of the pump).
The first thing to look at is when the machine is first powered on. No attempt is made here to copy the colours of the actual wiring by the way.
The mains power comes in through the IEC inlet on the underside of the machine (15) and is connected directly to the mains power switch (11). If this is switched on, the neon should light up the switch, and power will be connected to the controller (13) pins 1 and 3.
The controller then monitors the level probes in the water tank (14) and if there is no water in the tank, the controller leaves contact K1 in a position to feed the front panel neon (1) to indicate the tank is empty. The controller will do nothing else until the tank is filled.
When water is detected between the two plates in the water tank (14), contact K1 will changeover after about 1/2 sec. For this reason, if you turn the machine on with the tank full, you will see the neon light for about 1/2 sec.
With K1 switched over, power is provided to one side of K2, and out of controller pin 7 to the coffee switch (10) so a shot can be pulled (see later). Also at this time, the controller looks at the boiler probe (5) and looks for conductivity between this and the element earth wire. If there is no conductivity, it assumes the tank is not full, and so closes K2 to provide power to the pump (12) and to the fill solenoid (9). This allows the pump to pass water through the fill solenoid to the boiler. The solenoid on the group head is not powered, so the pumped water does not reach the coffee.
If the probe is faulty, the boiler might overfill, so the controller only allows the pump to operate for a few minutes at a time. When filling the boiler from empty, it will be necessary to switch the power off and then back on a few times to allow the boiler to completely fill.
When the probe detects the boiler is full, then contact K3 is closed. This allows the heating element to receive power via the pressure switch (4). This is a switch which is closed when the boiler pressure is below 1bar (14 PSI), and opens when it is above 1bar. By opening and closing as the pressure rises and falls, the pressure switch can keep the boiler at the same pressure and hence also temperature.
To prevent the boiler overheating if the pressure switch fails closed, or if contact K3 fails closed even thought there is no water in the boiler, an overheat thermostat is wired into the heating circuit (7).
If the boiler is not heating, the quickest way to diagnose it is to connect a multimeter between points A and B. You should see 230V AC. If not, the controller is most likely at fault. This sadly is the most common cause of failure, but is is quite easy to fix, costing around £65 for a controller which is just swapped with the original one.
If you do see 230V between A and B, then move the probes to between C and B. If you don’t see volts here, then the pressure switch is most likely at fault (about £20 to fix). To confirm this, move the probes to D and C. If you still don’t see volts, then the over-temperature switch is probably tripped or is faulty.
But if you do see volts between C and D, then the element is probably faulty (£60 – £100 to replace).
The final stage is pulling a shot. As discussed above, if there is water in the tank, K1 changes over and provides power to controller pin 7. This feeds the coffee switch (10).
When this switch is closed, it power the pump (green line), and the solenoid on the group head (8). This allows the pump to pump water through the heatexchanger inside the boiler, heating the cold water to around 100degC. The piping then routes it to the solenoid, which now open allows it to run through the coffee.
Finally, there is an 80W cartridge heater (6) which keeps the group head warm via thermostat (2) whenever the mains power switch is on.
We now stock the following items to maintain the TS:
Group head gaskets and screens
Group head heater thermostat (98degC)
Steam and water taps and spare washers
TS Commercial Steam Wand
Pressure Stat (pressure Switch)
Pump (Ulka EP5)
Standard commercial and Bottomless portafilters
Orman kl.1.6 Pressure Gauge
Steam and water tap knobs
On/Off and Coffee Switches