Glow worm Ultracom 24 firing issue

[MethodPH]

Went to a customer today their glow worm Ultracom 24 HE goes to fire up then cuts out turning the heating pump off, then does the same again before firing and running. Occasionally shows the flame is lit on display but flow temp doesn’t go much past 26. Then if you turn off and try again sometimes it fires up straight away and runs? Anyone have any ideas? I’m gas safe registered, but not for that long and haven’t done too many break downs

 

[ShaunCorbs]

flame sense prob ok ?

 

[MethodPH]

flame sense prob ok ?

Haven’t checked that but doesn’t even get to flame point, fan ramps up then cuts out does this two or three times before running

 

[ShaunCorbs]

Haven’t checked that but doesn’t even get to flame point, fan ramps up then cuts out does this two or three times before running

Aps then I would check first

 

[MethodPH]

Aps then I would check first

Aps?

 

[MethodPH]

Aps?

Ignore that air pressure sensor