vaillant ecotec no heating just water

[jaguar66]

Hi guys
Just want a bit of help can anyone help. One of my customers is having a problem with a vaillant eco tec that was fitted some 18 months ago . The boiller works normally on domestic hot water however fails to come on in heating mode no external controls are fitted . The boiler fires up on heating if you press the plus minus button but goes out after 10 mins or so displays code sf.h . If anyone can help it would be much appreciated I am g/s but only fit the things.:77:

 

[dave1]

The + and - buttons put into high rate so you can gas rate I think. Have you checked the temp control knob hasn't been snapped on the front and stuck on low?
No external controls? So you've got a link in at 3&4 on the board?

 

[RGII79]

check thermisters on ch side are ok also
flow turbine and diverter

 

[RGII79]

may have issue with high limit stat if you have just linked out and have no pump over run

 

[jaguar66]

Hi guys
Just want a bit of help can anyone help. One of my customers is having a problem with a vaillant eco tec that was fitted some 18 months ago . The boiller works normally on domestic hot water however fails to come on in heating mode no external controls are fitted . The boiler fires up on heating if you press the plus minus button but goes out after 10 mins or so displays code sf.h . If anyone can help it would be much appreciated I am g/s but only fit the things.:77:

yes the link is still there im hoping its just something minor that can be fixed easily .

 

[jaguar66]

Done all the usual basic checks gas supply dial turned up etc .Link still in place on the board. Thermistors i have not checked they have boiler specific values dont they when your testing for continuity???

 

[grahamgas]

If it is only 18 months old, then give the bunny a ring, two year warranty minimum on these

 

[Leo21]

Have you checked power across the link? No external controls, how about a built in programmer?

 

[arran197]

When you test the thermisters they have a resistance value, not continuity, that's for limit stats on older appliances. On the Vaillants, the dhw is PTC and the ch is NTC. As the temp increses, the PTC increses in resistance and the NTC is the opposite. If I'm honest it's unusual for one to fail. I would be looking at what ever switches the ch on if it works in service mode (SFH).

 

[jaguar66]

When you test the thermisters they have a resistance value, not continuity, that's for limit stats on older appliances. On the Vaillants, the dhw is PTC and the ch is NTC. As the temp increses, the PTC increses in resistance and the NTC is the opposite. If I'm honest it's unusual for one to fail. I would be looking at what ever switches the ch on if it works in service mode (SFH).

Thanks guys I have done a fault finding course at my local college but as I hardly ever carry out repairs im a novice and still learning. On the thermistors what does ntc mean and how do i test this I have an auto ranging test meter but im unsure what to do & do i still test this with no power on. I am told to persevere with the diagnostics side but i dont have anyone to bounce off except you guys any help is greatly appreciated.