Boiler Breakdown Checklist
If possible, tell the engineer in advance about how the boiler has been performing (rather than asking for a service when the boiler has broken down).
The first thing an engineer will do is turn the boiler on and check the controls. Informing the engineer of any possible noises, anything unusual or electrical work just completed will indicate possible areas where a problem might have occurred. Maybe new electrical work has changed the polarity on the boiler!
Arrange an appointment early in the day - if replacement parts are required this gives an opportunity to order them for next day delivery. The plumber’s merchant does not always have every part in stock. I worked for a service & repair company in France and they held thousands of euros in stock yet I still had to order parts, so think carefully about calling engineers out late at night or the weekend. You may still have to wait until Monday or Tuesday for parts.
Pressure jet oil boilers do not require the extensive range of parts needed by gas appliances, so there is a good chance that a dedicated oil technician will carry spares.
Before you call an engineer out do the basic and check that nothing is turned off that should be turned on. For oil installations and LPG check that you haven’t run out of fuel ; sounds silly but it happens. Check that the programmer is working correctly and that there is a demand for heat at the boiler. Read the boiler manual left with the appliance.