Vaillant Ecotec Plus Problem - New Boiler

[Vaillantman1997]

VM

Hi Guys

This is the first Vaillant i've fitted so thought I should make a post to try and get some help.

C/H isn't coming on - boiler status is 'S.30' (no heating demand from external controls - clamp 3-4 open).

I have linked out 3-4 but still the same.

Hot water works fine - full gas rate mode for commisioning also seems to work.

When loop testing for commisioning, fuse in spur blew. Replaced fuse in spur and fuse also pcb fuse - not sure if the 3-4 terminal issue could be related or not.

Any Vaillant experts out there who can give me some pointers? Need this system back on before monday!

many Thanks

Dave