Vaillant Pro24. No CH-Hot water ok.

[Fritzy]

Morning folks...calling all Vaillant combi experts!
I’ve got no CH. Hot water is ok.
No error code. Just like it’s switched off. Boiler has the panel mounted timer switch option. No stat. I took off the timer switch to see if that was the culprit-ch should default to ‘on’ if I remove this, right? No joy. Ch pump runs after hot water use as normal-I guess to dissipate excess heat? Ch flow pipe is warm under boiler but it switches off after a few seconds.
Thoughts?

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please see https://www.diynot.com/diy/threads/diy-gas.8090/

mod
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[Deleted member 267285]

Sounds a bit like a diverter issue. Which type do you have? Led’s or blue lit screen?

 

[Fritzy]

LEDs. I just went into diagnostic d35 (pos of diverter valve.) It’s staying at 100 (hot water) even after I turn off the tap...should it change to 0 (hot water)? Don’t want to jump to conclusions...but I’m thinking what else could it be?

 

[Fritzy]

Yep. I took the motor off the diverter valve and the central heating came on. Still reading 100 in d35 and the motor isn’t moving so I’m thinking the motor is shot...

 

[Deleted member 267285]

It should move to 0 when heating is on, but you shouldn’t be removing the cover on that appliance unless you can perform safety checks afterwards?

 

[Fritzy]

Hmmm
Diverter valve moves when I first power on the boiler but not after that...I’m still thinking it’s the motor-maybe not reporting back to the PCB-but not 100%...anyone wanna chip in with an opinion?

 

[The831Bunny]

You shouldn't be taking the front case off this boiler as it forms the room sealing aspect.

You can however easily check from the front panel: Check your heating temperature knob (if your model has it) alters the display temperature when you turn it, if the display doesn't alter, the heating knob spindle is broken. If you don't have knobs, set the flow temperature to 70C with the buttons.

Check your status code. Press the i button or navigate to the live monitor. S.30 is no demand from external controls (could indicate a PCB or link T3-T4 or 24V missing. S.31 is no demand from flow temperature request (clock duff or heating knob turned right down/broken).

Take the timeclock completely out of the fascia and try again, checking the status code.

If all else fails: Press the - and + together under the screen. It will fire the boiler in heating service mode for 15mins. If the rads get hot then the DV is fine.

 

[Fritzy]

Thanks for the reply 831 bunny, it's much appreciated. I hear and respect the note of caution in respect of opening the boiler.
Spindles are fine on the knobs.
yes, I'm getting s30 when I press the I
also the heating comes on when I press - and + together. the PCB is new...apparently tested-reconditioned.

 

[Fritzy]

Link T3-T4 is there.

 

[Fritzy]

OK. Full disclosure time-how I got here. I changed the PCB because I'd been getting intermittent f61 errors and temp display jumping up and down, but generally boiler was working fine. I figured it probably had nothing to do with the gas valve because CH was working ok, just hot water going cold and intermittent f61...must be PCB, right?
I bought a reconditioned PCB-fitted this and the hot water worked but CH didn't come on. Before I changed the PCB the CH had been fine. So I bought another PCB from the same supplier and have the same problem. No CH. The supplier swears both boards had been tested and work perfectly.
I press + and - together and the boiler fires up on service mode. rads get hot. If I press 'i' I see the s30 (no call for heat) message. are both these PCBs the problem, or am I missing something else?

There are NO external controls. just a timer switch on the front of the boiler.
any thoughts?

 

[denso13]

any thoughts?

With respect, you need to get this checked by a Gas Safe Registered person. You have been advised you should not have taken the front case off without proper testing when refitted and it turns out you have also changed the PCB. For any family/neighbours sake, get it looked at properly.

 

[The831Bunny]

Check D.8 diagnostic code (press i and + together). It should be 1 for heating controls calling (the T3-T4 link in your case) or 0 for not calling. If there’s 240v at T4 and no call, then it’s a duff PCB. Maybe a lesson in recon boards.