Throughout the shift or day, observe the following ...
Listen for any abnormal sounds coming from your machine ... example: hissing (steam); squeaking or scraping (pump or solenoid); rattling (loose plates or pump).
Smells - burning plastic; foul smell from steam wand or hot water spout -oohh boy !! ... that’s not good - call your coffee machine technician.
Look for brown discoloration in the hot water; leaks onto the counter top from under the machine.
Check when valves are closed that there's no leaks from the steam wand and hot water spout.
Site Glass (for machines fitted with a water level site glass) – check water level is correct usually half way between minimum and maximum marks on the face plate. If this is not checked continuously, the likelihood of your element burning out is very high.
Temperature Pressure - check the temperature pressure gauge, registers between 0.9 Bar and 1.3 Bar, this is often colour marked on the gauge dial.
Water Pressure - before dispensing water and the pump is not working, check that the water pressure gauge is registering between 2 Bar and 4 Bar. When dispensing coffee, or water is being pumped into the boiler, ie when the pump is working, the water pressure gauge should register anywhere between 7.5 Bar and 9 Bar.
Wear and Tear - check the filter cup rims or edges for damage. Check the grinder burrs occasionally for clogging, bearing in mind they can grind about 600 kgs of coffee beans before needing to be serviced.