I have a problem with the hot water on my 105e Instant Combi.
When I turn a hot water tap on, the boiler fires up and hot water flows, but not as hot as normal (I can easily keep my hand under it). If I watch the temperature LEDs, they climb to maximum and then the boiler cuts out with the flame and safety thermostat LEDs flashing - this takes around 20-30 seconds.
I can reset it and repeat.
Central heating works fine - temperature LEDs look good and no cut-out.
So it seems like the boiler thinks the hot water is hotter than it actually is.
I've checked the hot water thermistor resistance (at the PCB connector end after disconnecting) - it's 16 kohm with cold water running through and drops to 3-6 kohm when the water is hot. This seems reasonable. The manual says 11 kohm when cold so although there's a difference I suspect the thermistor is OK (if it was faulty a higher resistance would mean the boiler detects a colder-than-actual temperature).
For good measure I checked the safety thermostat and that is OK (close to 0 ohm). And anyway, if it was faulty I presume the CH would not work?
Any ideas? My best guess is a PCB problem but as that is quite expensive I thought I'd just check with those more knowledgeable than me!
Thanks in advance!
When I turn a hot water tap on, the boiler fires up and hot water flows, but not as hot as normal (I can easily keep my hand under it). If I watch the temperature LEDs, they climb to maximum and then the boiler cuts out with the flame and safety thermostat LEDs flashing - this takes around 20-30 seconds.
I can reset it and repeat.
Central heating works fine - temperature LEDs look good and no cut-out.
So it seems like the boiler thinks the hot water is hotter than it actually is.
I've checked the hot water thermistor resistance (at the PCB connector end after disconnecting) - it's 16 kohm with cold water running through and drops to 3-6 kohm when the water is hot. This seems reasonable. The manual says 11 kohm when cold so although there's a difference I suspect the thermistor is OK (if it was faulty a higher resistance would mean the boiler detects a colder-than-actual temperature).
For good measure I checked the safety thermostat and that is OK (close to 0 ohm). And anyway, if it was faulty I presume the CH would not work?
Any ideas? My best guess is a PCB problem but as that is quite expensive I thought I'd just check with those more knowledgeable than me!
Thanks in advance!
