when you select hot water only on the programmer does the boiler fire up and the pipe to the 3 port get hot?
as mentioned above you could try freeing the spindle but may be clogged/sludged up - may need a new 3 port.
as mentioned above - also do you have any line strainer in line or any isolation valves not quite open? check pump first, air in system. what's the heating thermostat on the boiler set to? heating thermistor/sensor has it been checked?
let me just clarify - i KNOW breakdowns are NOT easy!! I just wanted to point out to the OP that they are not all impossible if you are willing to learn to fault find / repair and train up
the only fault on board i had was a connection was loose so i just connected it back in - the other faults I had; thermistor faulty on DHW side, pressure problems, expansion vessel faults, pump faults, low water pressure switch faulty
no I am not. I have done non gas repairs though outside the boiler and some in ie thermistor, pressure, pcb etc - I'm not an expert of course but just was sticking up for OP!
when did I even say that?! People like you make me so annoyed - why get so aggressive? I don't go in merchants and say a jack I don't even go in merchants.
By the way - i DID NOT say anyone could do it and on the joint - I said I used hemp before.
course for a 28 year old vaillant?!! that's older than me! haha!! I didn't mean it to sound that way, just meant it's not impossible to find faults on boilers for engineers who can use a multimeter etc - the Original poster was a gas engineer.....
how have I be-littled it? I just said some posters make it out to be R.S, not all though. I apologise if I have offended you though.
I'm not saying it is easy, as said before.
having not read it all - if the noise is bugging the poster look and listen where's its' from - if it is the dc solenoid then have a closer inspect and if too bad replace - but i've not read whole post yet