Due Tec HE 28 intermittent hot water problem

[geofflove]

Boiler is about 5 years old. All fine until a couple of months ago...

Sometimes when taking a shower (Mira mixer) there is no hot water when shower is first put on. If left for a minute of two it will then come hot (this is MUCH longer than usual). Also sometimes during a shower the water will suddenly go cold (not heat to water at all) then after about a minute will return. This happens perhaps once every fourth shower on average. Unfortunately by time I run downstairs to look at the boiler and see what's going on it's running hot again so I can;t confirm which boiler lights etc are on - frustrating!

I'm pretty sure it isn't the shower itself. I don't believe the termo unit in it is suddenly moving and altering the themo on the shower makes no difference - there's just not hot there. I'm sure its the boiler. CH runs fine. It could be that there is a similar issue with hot water taps which just hasn't been noticed.

I'm wondering -

Could it be the turbine unit of the hall effect sensor sticking so the boiler thinks no water is flowing?
DHW temp sensor?

Any other suggestions? I think to swap the turbine on the hall effect sensor it's the whole inlet unit at about £90 - is that correct?

Any ideas on how to track this down?

 

[bazdaman]

Run a tap on full, what does the temp display say?

 

[geofflove]

Run a tap on full, what does the temp display say?

Ahhh, caught it at it this time.....

Got an e28 error. Dhw light was on but ignition light not on....... Turned tap off and tried again it came on fine again......

Ideas?

 

[geofflove]

A quick search suggests flue sensor error.

It's intermittent so guess could be wiring too. Is the sensor an easy change and a likely culprit for this?

 

[muggles]

Could be the sensor or could be a fault with the flue itself. Either way, this is getting into the realms of needing to call out a Gas Safe Registered boiler engineer to diagnose

 

[geofflove]

Just taken a look at the sensor - there is a tab/clip which holds the electrical connector in place. The tab appears to have broken off and the connection was therefore loose. Pushed connector on firmly and appears to be ok. I guess I might need a new sensor fitted to renew the clip and secure the cable properly with clip as it should be.

Cheers