Vaillant 282e Hot water fault

[lizard1975]

Hi, really hoping someone can help me work out the fault here, as it has me foxed.

The boiler works fine in central heating mode but is temperamental in hot water mode, The boiler recognises the call for hot water most but not all of the time and often tries to light repetitively with out success. It never enters lock out mode and after a few minutes of doing nothing will try to light again for a time. If it does manage to light then half the time it goes out after a minute or two and repeats the cycle.

Any ideas please?

 

[Agile]

If you studied some existing threads you might see that a blocked secondary heat exchanger is often the cause of these symptoms.

But thermal measurements of the components are needed to confirm this.

Tony

 

[lizard1975]

If you studied some existing threads you might see that a blocked secondary heat exchanger is often the cause of these symptoms.

But thermal measurements of the components are needed to confirm this.

Tony

Hi Tony,
Many thanks, I will strip down and check the heat plate exchanger first thing tomorow. I did try to measure the readings from the NTC sensor to see if it was faulty but without a table to compare the reading against, it was of little help. However due to the low cost of the part i replaced it anyhow, and whilst it did improve the running of the boiler (started to run correctly on the odd occusion compared to never before) i was still left with the above

 

[lizard1975]

Hi, found the fault. It wasn't the heat plate exchanger as Im getting a good 18c drop across it, but rather the micro switch that is not getting fully pressed down. Does this mean the diaphragm is on its way out or the micro switch as do they not normally need to be fully pressed? Have adjusted position of switch to give max press down by plastic lever