Ariston MircoCombi 23 MFFI hot water query

[Farenheit]

hi all
I have the above system, I know (old and not the best) however it has served me well, considering it was already fitted in the property when I moved in.
Earlier this year I had the main and secondary heat exchangers replaced by British Gas (long story - they didn’t need changing but as they were BG they insisted, however back then the problem still persisted so I didn’t get charged for it; it was a faulty expansion vessel in the end!)
Anyhow I currently have a problem where the hot water downstairs or upstairs is tepid even when the dial is cranked up to max.
Heating works fine.
I have narrowed it down to the temperature probe, however I have a query.
Do I need to drain the system down to remove it as I can see it is fitted near the secondary exchanger? This is so I have inhibiter at hand (added 2 bottles of Fernox F1 in October so will be gutted if I have to)
Also, does the lead on it come off easily? Do I just pull it off or is there a technique to it?
That’s it really.
Would appreciate the guidance as the lack of “hot” water is making for a quick bath at the moment

 

[Pickwickpick]

Are you gas safe registered?

 

[Farenheit]

Do you know of one in the Birmingham area that’s willing to do it? I have the replacement probe. Also I have a number for a local guy but he’s been avoiding my calls all week!

 

[Farenheit]

It’s possible it could be the diverter valve

 

[Riley]

It could be a number of things but seriously stop guessing and throwing parts at the problem and get another gas engineer. To be honest I’m guessing the conversation went “I need you to fit a temp probe to my boiler, it’s ok I’ll supply the part, I’m sure that’s the problem”?? Most engineers like to diagnose faults and supply their own parts that could be why he’s ignoring you