Problem with hot water system - worcester boiler

[grahamopey]

Hi there, I hope you can help me.

Over the weekend my Worcester 24CDI RSF boiler developed a fault where the central heating would run fine but the hot water would only run for a few minutes or even seconds before cutting out.
I consulted the manual and it advised me to check the flue for blockages, the sense tubes and the pressure sensor. I found the silicone sense tubes, feeding into the flue, had a build up of a white powder in them and were cracked.
For the time being I removed one line and the boiler ran fine (although this may be a little foolish), I intend to replace the tubing this evening and hopefully that will correct the problem, I do, however, have a few questions:

1. Do you think replacing the tubes will remedy the problem?

2. Is the white powder indicative of anything or is this common?

3. What is the best way to access the flu to check for blockages?

Many thanks

Graham

[peter the plumber]

You need to get an engineer out.

You have just put yourself and your family at risk from CO2 poisoning.

Leave a window open in the room with boiler it until its been check and try not to use it.

[muzza]

Do not attempt to fix this fault yourself, the carbon monoxide associated with boiler flues is lethal and may endanger yourself and you family. Get a CORGI registered engineer to check this out. I believe you have identified the problem but be safe before you operate the appliance