Hello, I have a Vaillant Ecomax VU 186E condensing gas boiler with an intermittant mystery fault. I'm hoping that with your collective experience, the following observations will point towards a single most likely common cause.
It all started 10 days ago when the central heating was switched to holiday mode for a week away, ie. programmed to maintain the house at a lower temperature with no hot water until the day prior to our return. The boiler had clearly failed to start up again at some time and now continues to remain obstinately unresponsive even when asked (politely) for heat! All program and thermostat controls appear functional.
These are the critical observations from switching off power supply: Power on and with demand for heat on. After a few seconds, with a few clicks the pump is running, the water temperature display becomes active but the fan does not kick in and therefore the gas fails to ignite. The pump then continues to over-run and will remain in that state for ever, it seems. Pressing the reset button simply stops everything and repeats the sequence again when the system is either hot, warm or cold.
However, just once in a while it contrarily decides to burst into life as if nothing was wrong and may heat continuously for several hours only to mysteriously stop burning, even though there is still demand for heat.
The boiler temperature setting is set high for winter, pressure is fine and all radiators and water cylinders are calling for heat ( as are we!). When working, diagnostic mode shows the fan speed fairly constant at around 175 when interrogated at the D 33 setting and the same figure comes up at D 34. Fault code either F30 or F32 shows when the boiler fails to operate (indicating "lack of air flow through the appliance"). The flue is clear, the condensate discharge is unobstructed and the fan has demonstrated that it can clearly work properly.
Now for the mystery clincher - exactly the same thing happened on 03/04/2009 and was cured (until now) with just unplugging and plugging in the fan sensor connection (smaller brown three wire plug connector on fan itself next to the white two wire power plug).... not so this year!
Something mechanical is my hunch, I've replaced the whole wiring tree just in case of a failed wire or connection and I've inspected all other wire connections. A pcb fault or capacitor would just go and not suddenly come back - wouldn't it?
Any ideas, checks or further questions guys will be very much appreciated.
It all started 10 days ago when the central heating was switched to holiday mode for a week away, ie. programmed to maintain the house at a lower temperature with no hot water until the day prior to our return. The boiler had clearly failed to start up again at some time and now continues to remain obstinately unresponsive even when asked (politely) for heat! All program and thermostat controls appear functional.
These are the critical observations from switching off power supply: Power on and with demand for heat on. After a few seconds, with a few clicks the pump is running, the water temperature display becomes active but the fan does not kick in and therefore the gas fails to ignite. The pump then continues to over-run and will remain in that state for ever, it seems. Pressing the reset button simply stops everything and repeats the sequence again when the system is either hot, warm or cold.
However, just once in a while it contrarily decides to burst into life as if nothing was wrong and may heat continuously for several hours only to mysteriously stop burning, even though there is still demand for heat.
The boiler temperature setting is set high for winter, pressure is fine and all radiators and water cylinders are calling for heat ( as are we!). When working, diagnostic mode shows the fan speed fairly constant at around 175 when interrogated at the D 33 setting and the same figure comes up at D 34. Fault code either F30 or F32 shows when the boiler fails to operate (indicating "lack of air flow through the appliance"). The flue is clear, the condensate discharge is unobstructed and the fan has demonstrated that it can clearly work properly.
Now for the mystery clincher - exactly the same thing happened on 03/04/2009 and was cured (until now) with just unplugging and plugging in the fan sensor connection (smaller brown three wire plug connector on fan itself next to the white two wire power plug).... not so this year!
Something mechanical is my hunch, I've replaced the whole wiring tree just in case of a failed wire or connection and I've inspected all other wire connections. A pcb fault or capacitor would just go and not suddenly come back - wouldn't it?
Any ideas, checks or further questions guys will be very much appreciated.
