DIY Doctor UK DIY Forums

i have a baxi 105e instant. i should explain that i recently had to have a leak in the boiler fixed. the boiler was drained to allow the repair. i have two problems but suspect they may be related.
problem 1) there is air in the system but i am not able to remove it. it bubbles into radiators - sometimes quite noisily - but when i try to bleed the radiator only water comes out; never any air. the air then seems to go on around the system. it bubbles into another rad. and then later into yet another and so on.
problem 2) when the c/h is on the temp. neons on the boiler all light up as expected and after 80C is reached the flame turns off. then ALL temp neons briefly switch off, the 80C neon (temp sensor) flashes a few times and then all neons come back on. there are sometimes variations on this theme but what i have described is the most common one.

is it possible for the trapped air to be causing a problem for the temp. sensor? whatever the answer, can you help me solve these problems?

a further thought. the boiler will often 'cycle' its heating - turn itself on and off then on and off again more than once in quick succession - when the lights are flashing. could this mean that what i thought were air bubbles was really boiling water.

Hi
Sounds like you have an air lock. If you have a look in the boiler, just above the pump there will be a small brass item with a small plastic screw in the top. This is the auto air vent The screw should be loose. If it is covered in green mess and to hard to move then you will need to get this replaced.

The reason why the boiler keeps cycling is because it heats the water to temp and as there is an air lock then it can't get rid of the heat through the radiators

Hope this helps

Paul