Baxi 105e (not instant)

[p the plumber]

Hi guys, this boiler seems popular at the moment, i had a prob today where central heating ok but open hot tap and microswitch activates fine by the diaphragm plunger and hot water comes out of tap for approx 10-15 secs then the 70c neon flashes which has a pic of a tap below it it and the water cools a bit then the cycle starts again. nothing in the book seems to explain this so im thinking either a sensor or pcb ? can anyone narrow this down? Ta P

 

[Billy Bob Bob]

try a ntc first,if not plate heat exchanger is it dumping down? (flow pipe hot when in dhw mode)also a sticking air switch will cause this try running with combustion door off

 

[diesel_ltd]

i would go for DHW NTC

 

[mikeygas]

Possiblly scaled up heat exchanger

 

[aggis]

Test dhw ntc approx 11 ohms cold, if 70degrees flashing, if out change.
If changed & doesn't work change w/w heat exch.
If no testing gear better start with ntc [cheaper] Or better still get a multi meter.