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.

 

[jaguar66]

now you mention it i think i can remember the tutor showing us how these thermisters are tested im just struggling to remember the process.

 

[M.Joshi]

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.

NTC - Negative Temperature Coefficient (Resistance decreases with increasing temperature)
PTC - Positive Temperature Coefficient (Resistance increases with increasing temperature)

Thermistor - Wikipedia, the free encyclopedia

Best to test the thermistor out of circuit i.e. with the wires/leads to the PCB removed. Otherwise you may be measuring other stray resistance.
You place your multimeter in resistance measuring mode (usually kohms) and touch the 2 multimeter probe tips either way round across the thermistor terminals.

 

[Leo21]

How can it be the thermistors if it works in test mode?

 

[jaguar66]

NTC - Negative Temperature Coefficient (Resistance decreases with increasing temperature)
PTC - Positive Temperature Coefficient (Resistance increases with increasing temperature)

Thermistor - Wikipedia, the free encyclopedia

Best to test the thermistor out of circuit i.e. with the wires/leads to the PCB removed. Otherwise you may be measuring other stray resistance.
You place your multimeter in resistance measuring mode (usually kohms) and touch the 2 multimeter probe tips either way round across the thermistor terminals.

Thanks for that I believe the customer has had a battle of wills with his wife over ownership of the switch one turns it up and the other turns it down I think that may be the problem ta..I will get back to you when ive been tommorrow.

 

[arran197]

To be honest with you mate, any combi's with no ch but hot water will most likely be an external control fault. Thermistor's rarely fail (with the exception of Ravenheats). It won't hurt to test a few when you go to the next boiler though, set your multimeter to ohms (the Omega style sign) and connect your leads to the prongs as described above. NTC you will see the resistance go down as temp rises and PTC the opposite.

 

[dancinplumba]

too much info in an open thread ????

 

[arran197]

Is this open to anyone? I thought the GSR forum was for those only registered? Not going to cause any serious issues testing a thermistor with a multimeter though I wouldn't have thought?

 

[jaguar66]

Thanks guys your help is much appreciated i will test a few.

 

[ambrosia]

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

its an ecotec only one thermistor/NTC
if the little radiator sign comes up then check the pump, it may no longer be strong enough to pump around the heating circuit, but enough to do the hot water

if there's no radiator sign then its not registering call for heating and could be pcb

 

[jaguar66]

Hi guys just a question
In regard to the heating control on this boiler im back tommoz to confirm the swith is fubard so if its not working at all and i remove the link between 3-4 and connect an external programmer will this overide the control on the boiler as the manual does not explain clearly enough either that or im too thick to understand it.

 

[Leo21]

Yep that's right, look in the wiring diagram in the book. It's quite simple, even I get it.

 

[jaguar66]

Yeh im looking at it on a disc but it says turn the boiler control for heat onto full but if its fubard i will still have the problem unless i link it out wont i ???? thanks

 

[Leo21]

Yes, does the boiler fire then shut down? If yes it's the divertor stuck on heating.

 

[jaguar66]

No works ok on hot water and fires up on heating when you overide the controls and displays code s.30 everything points to it being the switch thats not working.

 

[Leo21]

Link it out, and go from there.