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Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience:  Heating and hot water heating appliances experienced
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vaillant eco tec pro 24\28 hot water works fine central heating

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vaillant eco tec pro 24\28 hot water works fine central heating fires up then shuts down pressure is good water pump spins freely manually have changed remote thermostat hoping not the heat exchanger no fault codes showing
JamesInch :

Hi, you mentioned you change the remote thermostat, what make and model is it?
Have you set the C/H on the controller to "always on"?
It sounds like the controller isnt calling for heat, if you turn the thermostat down then a minute later up does the boiler start?
Another item to look at is the C/H actuator, which lets the hot water from the boiler flow past the radiators, if this isnt working the boiler is heating a small loop and reaches critical temperature very quickly, you could try manually opening the actuator to let the water flow.
The fault your describing doesnt sound like a thermal couple \ heat exchanger fault to me.

Hi . Your boiler is a combination boiler. There are a couple of things it could be, your heating thermister/thermostat could be faulty and is the easiest thing to change. Could be a fault with the diverter valve , but just need to check a couple of things with you first
Customer: replied 3 years ago.

have changed thermostat and no change i think more than likely diverter valve as there is a clicking sound as if something is trying to engage heat seems to get as far as the pump and a little further have just cleaned pump and all seems in order ?

Definitely sounds like the diverter . take the head off and see if there's any movement inside
Customer: replied 3 years ago.

sadly diverter valve very scaled up no movement have cleaned to my best and sprayed with wd40 I'm going to pressurise the system and hope it holds water !!!! ?

Wow,hopefully that will sort it
Customer: replied 3 years ago.

fired up well sadely has fast drip from diverter think because i had trouble lining up pin on diverter ?

Maybe some silicon grease on o ring ,or at worse a new o ring
Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience: Heating and hot water heating appliances experienced
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Customer: replied 3 years ago.

i can't get the central pin out but what about ptfe past or pumbers mate with a5 mill rubber washer on top ?

Have a try , but you don't want a call back ,if you can afford it I would just replace it . maybe PTFE , buy I wouldn't use plumbers mate anywhere near the boiler, just in case you get some in the system. The fast drip has to be an o ring somewhere .