We have a Vaillant Sine18 combi boiler. Been in the house 4 years and it's just gone wrong for the third time. No hot water or heating. No main burners.
The first problem 3 years ago was the pilot light not staying lit, which turned out to be due to the barbed spring in the flame failure unit not catching, easily fixed, but took a week to find. Then last year, it blew the fuse on the control PCB, which I replaced and it worked for another 9 months until Sunday morning when the fuse blew again. This time a new fuse blows instantly so I've looked at the electronics a bit closer. I removed the control PCB (without disturbing the gas side of things...I am not CORGI, but am a qualified Electronics Engineer). The rectifier was pretty burnt so I replaced that, but still the fuse blows. I was reliably informed by "an ex Vaillant engineer" that this is a common problem due to moisture on the solonoid and the fuse should be 2A (seems very high to me for mains current! That's approx 500W!). The fuse I put in last year was 1A, and now a 1.6A blows. The pump is not downstream of the fuse, only the solonoid driver circuit. The fuse blows even with the solonoid disconnected, so I have diagnosed a faulty trainsformer. Anyone agree? The primary winding resistance is healthy (a can't remember what it is but prob 50ohms or so), but the secondary winding is 0.3ohms which seems a bit low. The solonoid is 23ohms which I'm pretty sure is correct. Anyone know what voltage the solonoid runs at? I seem to remember 15V from my probings last year.
I've ordered a new control board, but I'm worried that there is more to this than just the board. Why did it blow in the first place? Does that control board low voltage drive anything apart from the solonoid? Does the control board only power up when hw/heating is demanded, or should it be powered all the time? The fuse blows when hot tap opened or heating clicked on at thermostat.
The house is so cold my wife has taken the baby and cat and moved to her mother's! I need to fix this asap! Would appreciate any comments if you know these boilers, thanks in advance!
Scott
The first problem 3 years ago was the pilot light not staying lit, which turned out to be due to the barbed spring in the flame failure unit not catching, easily fixed, but took a week to find. Then last year, it blew the fuse on the control PCB, which I replaced and it worked for another 9 months until Sunday morning when the fuse blew again. This time a new fuse blows instantly so I've looked at the electronics a bit closer. I removed the control PCB (without disturbing the gas side of things...I am not CORGI, but am a qualified Electronics Engineer). The rectifier was pretty burnt so I replaced that, but still the fuse blows. I was reliably informed by "an ex Vaillant engineer" that this is a common problem due to moisture on the solonoid and the fuse should be 2A (seems very high to me for mains current! That's approx 500W!). The fuse I put in last year was 1A, and now a 1.6A blows. The pump is not downstream of the fuse, only the solonoid driver circuit. The fuse blows even with the solonoid disconnected, so I have diagnosed a faulty trainsformer. Anyone agree? The primary winding resistance is healthy (a can't remember what it is but prob 50ohms or so), but the secondary winding is 0.3ohms which seems a bit low. The solonoid is 23ohms which I'm pretty sure is correct. Anyone know what voltage the solonoid runs at? I seem to remember 15V from my probings last year.
I've ordered a new control board, but I'm worried that there is more to this than just the board. Why did it blow in the first place? Does that control board low voltage drive anything apart from the solonoid? Does the control board only power up when hw/heating is demanded, or should it be powered all the time? The fuse blows when hot tap opened or heating clicked on at thermostat.
The house is so cold my wife has taken the baby and cat and moved to her mother's! I need to fix this asap! Would appreciate any comments if you know these boilers, thanks in advance!
Scott