Glow worm 38cxi hot water pain

[Richie_77]

Hi all went to one of these the other day and it's got me scratching my head.

The hot water temp was fluctuating greatly, running hot cold with the boiler cutting in and out.

Took the plate heat ex out gave it a bath in some nasty acid I've got, usually does the trick puts the it back and still the same maybe a mild improvement.

So thinks ok maybe the the thermistor readings are about right but just to double check I take it off the hot water pipe and boiler works a treat.

So starting thinking the thermistor is iffy so I change it, Hot water still not overly hot and boiler running on low rate.

Any ideas would be greatly appreciated.

Thanks

Rich

 

[kb76]

Does it have the rubber linking tube off the main heat ex on left hand side. These choke up and usually feels very hard. Filter further down before it enters the block also

 

[Richie_77]

Not that I recall, But if that was the case why when I take off the hot water thermistor the boiler works faultlessly.
The heating also works fine.

 

[kb76]

If no blockages, check flow switch is operating correctly and dc voltages are correct on the 3 wires to J7 from memory. Might be pre heating when thermistor is disconnected