Viessman Vitocrossal 200 CM2 186

Jalen_Jalen2006

Fault Code D4, annual maintenance ran the boiler to high limit. Ever since then it’s been just running the fan, tech support told me it would do it until it cools the heat exchanger but it’s been a few weeks. Heating season now boiler is still D4 and running fan.

GGross

Depending on your control there are different steps to take. if you know which control you have that can be a start, essentially D4 is showing the fixed high limit has tripped, if you can't reset the code once the boiler has cooled down there are different steps to take to check the fixed high limit depending on your control

Jalen_Jalen2006

https://forum.heatinghelp.com/discussion/comment/1811912#Comment_1811912

we have a vitotronic 100 GC1

GGross

There is a fuse marked location F2, check that it has not blown, and check if the fixed high limit is actually open still.

GGross

I believe the safety for high limit is the 151 plug but confirm that with your manual

Jalen_Jalen2006

https://forum.heatinghelp.com/discussion/comment/1811921#Comment_1811921

I’m sorry would it be inside the control trying to find where that would be or is there a picture of how it may look.

Jalen_Jalen2006

GGross

Check fuse F2 first if you haven't already

Alan (California Radiant) Forbes

@GGross Do you want him to check the 151 plug for continuity? And I can see the F2 fuse location on the face of the control.

GGross

https://forum.heatinghelp.com/discussion/comment/1811986#Comment_1811986

Yes, I am fairly sure that's where the fixed high limit connects to the board. Hoping its just a blown fuse, that would raise the question of why it blew though.