This tutorial goes with Boiler elements, Pressure stats and overtemperature trips.
Boiler not heating.
It goes without saying make sure the machine is isolated from both the mains electricity and water supply before dismantling.
There are possibly 3 or 4 reasons the boiler will not heat, the first one is the power supply switch failed although if the rest of the machine is working E.G. the pump when calling for coffee then the switch is fine.
The pressure switch can fail, these fail normal due to the contacts burning away after years of service, to check the pressure switch you will need to measure the voltage using a multi meter on the output side.
The pressure switch can also fail if the element blows although this is not common these days with sensitive supply trips.
The next possible cause is the element itself, the only way to test the element is again with a multi meter, this time on the ohm’s reading scale to check for continuity in each element, you should have a reading of, well it depends on the actual wattage of the element, what you don’t want is zero or open circuit.
If it is open circuit it will need replacing, this is not a job for inside a café or kitchen unless the machine can be placed over a sink draining board as once the element is removed it will flood.
When fitting a new element make sure the surface is clean, a thin covering of a high temperature gasket sealer can be used for cardboard gaskets although we recommend using Teflon gaskets as these will not stick and should it need replacing again it the future will save time.
If a Teflon gasket is used do not over tighten the nuts or bolts holding the element, once the machine has heated it is recommended to tighten them a ¼ of a turn.
The last cause (this only applies to machines where one is fitted) is the over temperature trip tripping or failing, if just failed then it needs replacing, if it’s tripped then the pressure switch should be replaced as the contacts can weld together causing the machine to overheat, however this is a symptom of the element drawing a high current, possibly due to an earth leakage.
The temperature trip tripping can lead to the replacement of the element and the pressure switch, to replace both would be a good precaution especially if the machine is urgently required for service.
What causes earth leakage? Limescale build up on the element isolates the copper of the element from contact with the water, this causes hot spots which over time will fail and can cause the element to leak current into the water, this is not a big enough leak to cause any trips to blow but is enough to overheat the contacts of the pressure switch and even the over temperature trip over a period of time.